When i open any post on the site without actually logging in, at the end of the post there is a survey question "Was this post useful to you ?" with an yes/no type of choice to answer. I wonder what happens when we click on yes/no. Is this data displayed anywhere, and what is it used for ?
See these threads on meta.SO:
explaining that there is not much to it at the moment, but there might be in the future. At the moment the anonymous feedback is just collected.
Users with more than 10k reputation can explore the stats here. I don't know if these or similar statistics are visible to users with lower reputation.
Added: (April 9, 2012)
for example (I haven't tested them).