I've been meaning to say something about Patrick Dempsey's departure from Grey's Anatomy, I find it more interesting that they may wind up cashiering all of the original characters.
You can argue whether or not the show would survive without Dempsey (though I think losing Ellen Pompeo, whose character the show is named for, is a bigger problem). But losing just a significant chunk of original characters makes me think of those last, lame years of prime time soaps like Dallas and, even more chilling, the entirely unnecessary last season of Scrubs.
This is a case where a large-scale cast change should either trigger a new series (such as how The Practice begat Boston Legal) or a wrapping up of the show entirely. Shonda Rhimes shows no remorse when killing off characters, and I hope she'll be similarly decisive when it comes time to determine the fate of the entire show.
