About ten years ago I was asked to be godfather to the new son of some in-laws I didn’t know very well. These jobs went in a strict rotation in my then-wife’s family, and it was our turn at the font. I agreed to serve but worried about one problem: I was having the worst trouble remembering the little tyke’s intended name.

(I still have that trouble. Either he was meant to be Jason and I kept calling him Nathan, or the other way around.)

Anyway, I had about two months in which to train myself. I studied hard, practiced often and corrected myself whenever I caught myself starting to give the wrong monicker.

You guessed it. Two months later of rehearsals later, and with basically two jobs during the baptism—give the child’s name correctly and keep his fruity white dress out of the water—I stepped out and in a loud, firm tone, said the wrong name.

So I can empathize with the plight of Dr Pepper, which blew Sunday’s Guns N’ Roses soda giveaway despite more than half a year to prepare.

The company hooked into a gimmick last March by offering a free Dr Pepper to every American if GNR released its long-awaited album “Chinese Democracy” this year. And when Geffen Records confirmed in October that the album would finally see the fluorescent light of retail day on Nov. 23, Dr Pepper reaffirmed its intention to make with the free soda. All claimants had to do, it said, was to go to www.DrPepper.com between 12:01 a.m. Sunday and the same time Monday Nov. 24 to get a coupon good for a 20-ounce Dr Pepper on the house.

Except, not. In what might be an object lesson in the perils of underestimating Web traffic, visitors to the Web site on Sunday reported a variety of error messages that added up to what one blogger described as a ‘greatest hits of server breakdowns”: everything from “Service Unavailable” to “not enough storage is available to process this command.”

Apparently anyone who made it in to the site was in for another shock, since the coupon sign-up ran so slowly that many users’ browsers timed out again and again.

And when those users turned in frustration to the toll-free number listed on the Web site—yep, they jammed the phone lines. And remember, this offer was supposed to be available for only 24 hours, so as the day went along, people got more frantic.

The debacle “makes [Dr Pepper] look kind of bad now but rest assured that they’ll have a notice up tomorrow saying ‘We’re thrilled with the response we got!’ instead of ‘We weren’t prepared to have that damn album come out and have to make good on our promise!’” blogged Jason Gross on PopMatters.com on Sunday.

And sure enough, at 12:38 EST on Monday, a release crossed the wires saying that due to “tremendous consumer response”, Dr Pepper Snapple Group was stretching out the coupon giveaway until 6 p.m. EST.

“People are passionate about Dr Pepper,” marketing VP Tony Jacobs said in the release. “The response has been greater than anticipated and we want to do everything we can to ensure Dr Pepper fans get their free coupon. As a result, we’ve extended the offer, increased our server capacity and added a toll-free number.”

I don’t share Gross’ belief that Dr Pepper never expected to have to honor the free soda offer. But I do think they didn’t think through what that offer would entail mechanically. Perhaps they really just didn’t expect so many people would be drawn by the offer.

Wrong, wrong, wrong. As the Los Angeles Times entertainment blog pointed out, by mid-afternoon yesterday seven of the top 10 searches tracked by Google Trends were for some form of the keyword “Dr Pepper”. Meanwhile only one of those 10 searches mentioned Guns N’ Roses, and one other mentioned the album title.

That’s a wave of determined consumers looking for a specific Web site. Too bad when they got there, the Doctor was out, technologically speaking.

I tend to think instead that the good folks at Dr Pepper were so intent on the undeniable PR bump they were hoping to get with this offer that they forgot to do the basic blocking and tackling of Web management. Maybe they underestimated the computing capacity they’d need to serve the registration page up to so many people simultaneously; maybe they thought traffic would come through in a steady stream and weren’t prepared for a spike in logins during halftime in Sunday afternoon football or something.

Stuff like test-driving server capacity is going to be more and more a necessary part of implementing an online promotion. As campaigns come to rely on viral spread and word of mouth, it may be increasingly difficult to tell in advance how many people will respond. Add a tight time limit to that indeterminate audience, and you could find yourself in the middle of a stampede to your Web site.

From a failure to run those pre-checks, the Doctor bungled what could have been a very nice high-visibility promotion and gave rise instead to a lot of consumer frustration and a handful of conspiracy theories. It will be interesting to see how many registrations Dr Pepper gets before time runs out tonight on the offer. I’d be willing to bet a large number of would-be soda fans gave up when they couldn’t get through yesterday and are now telling friends online and in real life how they got shafted out of a free drink by Dr Pepper.

Nathan/Jason, I hope you’re not one of them.

UPDATE: The day after this post, Dr Pepper got a letter from Axl’s lawyers blaming the company for an “appaling fialure to make good on a promise it made to the American public.” The letter asked for an extension of the free-soda coupon offer, a public apology to GNR fans in full-page ads in the major newspapers, and oh yes, some financial compensation for hooking into the hype around the “Chinese Democracy” release.

That last is an interesting development, since the band’s only response after Dr Pepper made its public soda offering back in March 26 was the following release from Rose:

“We are surprised and very happy to have the support of Dr Pepper with our album “Chinese Democracy,” as for us, this came totally out of the blue. If there is any involvement with this promotion by our record company or others, we are unaware of such at this time. And as some of [former GNR guitarist]Buckethead’s performances are on our album, I’ll share my Dr Pepper with him.”

But eight months later, the lawyers weigh in with demands of recompense for “unauthorized use and abuse of their publicity and intellectual property rights.”

At a Promotional Marketing Association legal conference in Chicago a week ago, Joseph Lewczak, a partner at Davis & Gilbert LLP, set up a hypothetical case of a razor brand getting visibility by starting a Web site to encourage the two bearded guys from ZZTop to shave for charity. His recommendation was that if the brand didn’t get advance permission from the band’s management, they might be liable for trademark infringement. I asked about similarities between that and the Dr Pepper/Guns N’ Roses example, and the panel– including VP and GC Gabe Karp of ePrize and Po Yi, VP and chief advertising counsel for American Express Travel Related Services– seemed to conclude that Dr Pepper probably would have done well to have a formal agreement in place before taking advantage of the publicity surrounding the album release.

Press reports quote Axl Rose’s lawyers to the effect that they tried to negotiate a better couponing arrangement after last Sunday’s server breakdown, but that Dr Pepper had resisted.

For its part, Dr Pepper issued a statement noting only that this stunt was “one of the largest responses we have ever received for a giveaway” and that “we’re happy we were able to satisfy the thirst of so many Dr Pepper fans.”

That’s truly putting a happy face on what really has become a dog’s breakfast of a promotional mess.