just how do you get a million bucks for playing games?

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recently, i saw on the news about the louisiana man who became a millionaire just by playing MLB online. i wonder how this works.. i mean, i heard somethings about it before, but i never get to find out how. has anybody here who's into online gaming and winning some real cash? i'm not sure if i'm going to try it. it just got me curious. thanks.