My work has comment cards that we pass out at the end of each customers' visit. Management and the owner are pushing these heavily, on both ends. They advertize that by filling out the card, the customer is entered into a draw for $50, draws held monthly. They also keep track of how many cards each server gets filled out during each shift. All though they do pay attention to the comments, and have made changes to the menu as a result of them in the past, the main intent is to collect e-mail addresses. They send out waaaay too many e-mails about events and specials, which most people find irritating. But I suppose if they get even a few people to return, it's worth it in their eyes.
In any case, hardly anyone takes these cards seriously. Most cards just say "shorter skirts", "bigger boobs", and "free drinks". Some get pretty hilarious though. A whole table filled their cards with sexual comments about a male manager, asking if the bulge in his pants is a sock shoved down there, calling him "dreamy" and asking what he's doing later. We all had quite the laugh. I get a few cards saying I should be cloned, which is always nice, and I even had a lovely date the other night with a guy who left his number and a note to give him a call!