In this case, I can't imagine the Twitter details include much more than email and ip addresses. What I'd be worried about is what happens afterwards, when they order Google and Microsoft to hand over your emails and chat logs.
Call me crazy, but I don't think the US Government should have access to such private information of foreign citizens, even if it's hosted in US. At the very least, it should be their own national Governments that should be able to request for it, and only if their own laws allow it.
This will only promote anti-Americanism, as people will try to stay away from American services. Who knows how far they will they take this. If I "support" #OccupyWallStreet on Twitter, does that mean that one day they might come after me, too? I really can't be sure either way these days, which means I can't treat things like these too lightly.
The story is actually about the european courts granting the U.S. authority to request information on their citizen. While I don't expect the U.S. courts will put up much of a roadblock (they rarely do), The DoJ will still have to go through the U.S. process to get the desired information.
