Om blogs here about the general trend lately of one company copying another, copying another, copying another, ad nauseam. This most likely began when Google came along and looked at a field that was essentially dead, (search, and then eventually advertising) and then waltzed in and proceeded to dominate it.
I think this flipped the light on in everyone's head that, on the Internet, if you can do something better than everyone else and get some mind share, you can leapfrog them, seemingly overnight. I think we're just seeing this process continue to accelerate. Now people are trying to copycat before the site they're copying has even launched. Hopefully we'll continue along this path to it's natural end, where an infinite variety of all possible Web 2.0 ideas will all be launched simultaneously. I hope that I have the good sense to start a server farm before that day comes.