In my experience, that line is pretty fuzzy in this business. E.g., take all the various mafia games on facebook, myspace, iphone, and now twitter. They're more

In my experience, that line is pretty fuzzy in this business. E.g., take all the various mafia games on facebook, myspace, iphone, and now twitter. They're more or less all knockoffs of one another, but nobody seems to care. In fact, consumers seem to love them all. In this case, shame on twitvid.com for using the exact same name (and filing a trademark application for it), but I think copying features and design elements is fair game. Ultimately the one that provides the best service will win.