anybody do walmart survey?

[thetop31]

everytime I shop walmart, I use the receipt doing the online survey, and see if they really have 5,000 prize, but never win.
then I wonder if it is true that walmart do the sweeptakes? anybody win? if so every 3 months they send 5,000 prize, then how much profit they make?
even  I know some other website use this do scam.... it is start again, now From August 1, 2011 and ends on October 31, 2011. I doubt,I do not think I will do it again.