It seems to depend on which Best Buy you go to and if you have returned other receiptless items in the past 12 months.
I went to one Best Buy with my video game and they shot me down. I went to another BB in a more upscale neighborhood and they gave me a store credit (after getting manager...
I don't know about self-advertising but SD has huge threads on sites like ipodsweepstakes and yourfree360games so they seem to allow talk about sites like yours as long as referrals aren't discussed.
Volition has a get paid page in their forums and I don't know how it is now but in the past if...
My old roommate used to do a lot of these types of sites and joined a lot of them from volition.com's forums. You could start a thread there telling about your site. You could probably a start a thread at slickdeals as long as there is no referral link (which of course you wouldn't need anyway).