Feedback forms are, I would say, a classic case of a 'good text-book idea'. That is to say that everyone knows that one should seek feedback, and try to act upon it, as a means of improving one's product.

I have, however, always had my doubts as to whether or not they are ever going to give you a 'true' picture of users' views on/problems with a website when used in isolation.
 
It's a bit like when TV channels screen a program, and 12 people phone in to complain - the company will always (justifiably) say that there were 10 million other people watching who DIDN'T complain.

This doesn't, of course, mean that the 10 million viewers were actively happy with the program...nor that their views (were they asked to give them) would correspond to those of the 12 complainers. All that it means is that the 12 can not be assumed to be representative of the 10 million - especially as they are a 'self-selected' group.

Indeed, one could argue that anyone who had enough time and energy to fill in a 'feedback form' was highly unlikely to accurately represent the views/profile of the 'general user population', in so much that the 'classic' responses to problems using a product is to discard or modify it.

The most important issues with one's product - if one chooses to classify these as those which cause the most amount of inconvenience/irritation to the most number of people - might, therefore, be better identified through system logs, conversion rates and usability testing.

I suppose all of this was, then, just a drawn-out way of saying a similar thing to that which everyone knows - that gathering as much data about what people really think of, and how they react to, your current product is the best basis for future revisions to that product.

I can't really see how including a 'feedback form' could do any harm as long as it:
- was voluntary;
- wasn't presented to the customer at a point at which it would interfere with an ongoing task;
- clearly explained its purpose
- gave an alternative help/complaints phone number if at all possible
- didn't take long to download
(all feedback forms should also, ideally, receive a personal response from an appropriate individual within the organisation)

So the message to take home with you and have sleep at your feet? Use feedback forms by all means, and respond directly to them whenever you can, but don't rely upon them as your sole source of feedback!

best,
t