I'll have to echo socrates, at least for some properties.

I try to be pretty conscientious about completing the surveys if I receive them, and have two experiences to confirm that (at least sometimes) they are read and acted upon.

One was from a stay at a Renaissance and I mentioned a deficiency I had noticed. I got a nice e-mail from the manager of the property discussing the point, and noting that it had been corrected, and expressed a hope I'd have a chance to see that for myself at a future stay.

The other was at a property where they know me. I really like the service and the staff there, and gave them a glowing commendation in the survey. The next time I stayed at the property, the manager saw me and thanked me for the comments. I told her it was just what they deserved, and said it was nice they actually read the surveys. She said she personally reads every one, and mentioned that the surveys have a direct impact on bonuses.

I don't know if it's the same for all hotel chains, though. I also answer surveys from Starwood properties and don't recall ever getting any feedback from them. And I don't recall ever getting a survey from a stay with the Hilton chain (although I may have).