FORTUNE -- The Internet may be a wonderful thing, but no one should expect sunshine and rainbows when asking for its honest opinion. Read an uncensored comment stream on pretty much any post, blog or video, and its clear that the Web provides people with, among other services, space to criticize, constructively or otherwise. So McDonald's (MCD) should have known better when it got knocked on its heels after launching a Twitter campaign on January 24. The idea wasn't a bad one -- pay for a couple of promoted tweets encouraging customers to get in touch with farmers. First, the company pushed the hashtag #meetthefarmers. But in the middle of the campaign, the fast-food goliath introduced the hashtag #McDStories, hoping to stir up good press about consumers' experience at its restaurants. The first hashtag was saying, "Here are the great people who make our potatoes." The second says, "Tell us what you think of us," which, in the Web world, is risky business.