Taking down content when a copyright holder complains is what they *have to do* - auto-scanning the audio of all submitted content and comparing it to a massive library of known copyrighted materials with such poor sensitivity that they mistake a DnB remix of a song for the original... that's something they choose to do.
The alternative would be a huge amount of staff, in various languages, to review every single copyright complaint thoroughly to ensure all videos are in proper accordance with local copyright law. This would be great for creating jobs, but, frankly, this would be extremely expensive.
On another note, I personally completely reject copyright and release all of my creative work under a very loose creative commons license or public domain. So there's always copyright supporters (in this case, the music industry) to direct general annoyance toward
So Google doesn't have to, it simply chooses to comply in order to have the path of least resistance.
Imagine if Google was in Sweden. I'm pretty sure they would have an army of lawyers ready to eat up any legal threats from the US.
No, Google doesn't have to, just like I don't have to pay taxes. It's all a mind game, really. If Google wanted, they could join me and my rag-tag gang of liberty lovers and go all out on America's oppressive regime
So far, they don't seem all together interested, outside of a dislike of SOPA and CISPA (I could be wrong about CISPA...) Anyway, we all know what happens down this road, and it's never fun. It can make life Hell, actually--more than it already is, anyhow.