after getting significant points with socialrewards (see the thread in comps) , I just signed up for topguest. This has facebook, twitter, foursquare and other components. I figure that while I check-in with Foursquare, I could get credits here too. I don't know much about the program, so I can't comment. Its possible that the Luxor is in both programs.
Not that I'm complaining, because I really thought I'd get spammed, but I haven't received 1 text from them so far. They promoted signing up pretty well and then nothing. I was just looking for another avenue for deals.
I have been on and off with various MGM hotels. Never seen any great offers. Very easy to stop it when you run out of money and head home.