[Update: Xbox Live director of policy and enforcement later tweeted that, after double-checking with Activision, Modern Warfare 3 pre-release play is not authorized, and asked that gamers be patient.]
A Kmart in Tampa, Fl broke Modern Warfare 3's street date today, a whole five days beforehand, and some gamers were able to take advantage of the sale.
Obviously, copies have already hit eBay and Craigslist at insane prices, with eBay hitting the $500 mark.
Those who manage to pick up their copy either at a Kmart or through a third-party can rest easy when playing online--on Xbox Live, anyway--as Xbox Live director of policy and enforcement Stephen Toulouse tweeted if your copy is legit, you can go ahead and have fun.
Those who have an illegally downloaded copy, on the other hand, will surely be banned when caught on Xbox Live.