I stepped out of the office today to see how marketers can give away free food without Oprah Winfrey’s help.

The event was a sampling session for a new product, Flatbread Melts, launching today from DiGiorno, a Kraft division. And it was a good reminder of how very simple it can be to get a new food item into tasters’ hands for free—with, perhaps, a few caveats and concerns.

The tasting was held for two hours on a plaza where Michigan Avenue meets the Chicago River. At the request of agency Wunderman, Chicago-based Kaleidoscope had designed and installed a clever eating area with stand-up tables and three benches dressed like the wedge-shaped flatbreads complete with filling. The microwaveable Flatbread Melts are designed to be single-serve items, but as furniture they could accommodate three very comfortably.

Not that many people were doing any sitting: Most were getting their toasted flatbread and heading back on their way. Appropriate, because mobility is apparently what Kraft wants people to associate with the new handheld sandwich.

One clever idea associated with this street tasting was a small fleet of pedicabs carrying signs that said “Hop In for a Free Lunch”, or something to that effect, and carried the DiGiorno logo prominently on their sides. It seemed a good way to spread word of the giveaway quickly to the cross-streets and other lunchtime centers on a sunny Chicago day. I’m told Wunderman supplied 15 pedicabs for the event, working about 10 to 2 p.m. to bring people from surrounding neighborhoods.

But shortly after the noon kick-off for the sampling, the line for free food was about a block long, and I wondered about the reaction from folks in the pedicabs when they saw that they were in for a goodly wait to get that free food. I didn’t actually hear any grumbling, but I know dismay when I see it, and many of those folks were evincing it—as if they might have chosen to stay where they’d been and get their lunch faster, if less cheaply.

That wasn’t the only issue I identified with the giveaway. Another problem is probably a constant in urban America today, and live-events companies must handle it all the time, but I hadn’t seen it so obviously in action before. When you give away free food in a downtown area, you get a lot of indigent or homeless people.

A lot. As in, perhaps one in three or one in four people on line the three times I checked the crowd during the two-hour event.

Let me be clear. These people obviously deserve to be treated the same as any other consumer, and in fact deserve free food even more than most. But chances are slim that many of these folks will then be buying what they’re given to sample.

And I found myself wondering if live-event companies need to guarantee that a certain proportion of the product giveaways go to tasters who can reasonably be expected then to turn into customers. One way to minimize the problem, I presume, is to set up in commuter-heavy locations. But in this instance, sampling was happening only in one spot, in a public plaza far from trains or el stops and under the stern gaze of a statue takeoff on “American Gothic”.

Is there some live-event ROI rule of thumb applied when only 75 of one hundred samples given away go to consumers with disposable income?

Adding to the down-at-heels feel of the event, another sampling was going on in the same plaza at the same time: free samples of a gourmet cat food I won’t name. It was sheer—but uncomfortable—coincidence.

Yes, a lot of the indigent-looking folks in the DiGiorno line were holding two sample tins of cat food. And no, they didn’t strike me as pet-owners.

I’ll say it explicitly: If this “free food” trend continues, companies using the tactic might want to consider making donations to local food banks or shelter charities to offset the impression that they’re manipulating the needs of the public.

After all, most of us have plenty of food without the free. Running these giveaways has the effect of making clear to us all how many people in this country are seriously in want. And brands may have to start fighting the perception that they’re just tossing out free chicken, or sandwiches, or whatever to the crowds to watch people scramble.

But from a strict marketing perspective, I’m curious what calculations apply to judge the success of sampling events in cases like this, where a sizeable proportion of the product went to non-prospects. Is that just an incidental cost to the brand- and awareness-building function of seeing the signs and the crowds? If anyone can enlighten me, I’d love to hear more.

By one metric, however, this simple DiGiorno tasting was a hit: They had enough food, nobody threatened a sit-in, and no CEOs had to go on TV or YouTube the next day to clean up a PR mess. That was a refreshing change.

Are you listening, KFC, Popeyes and Quizno’s?