Also P2P traffic is often monitored by your ISP and if they decide you are using excessive bandwidth for P2P (even legally) they can (and some do) reduce your connection speed
And when you download stuff by P2P you are downloading it from other users, not from an official site so there is always a chance that what your downloading is not what you think it is!.
It is one of the most unsafe things you can do.You open yourself up to downloading virus',videos that aren't what they say they are(could end up with chld porn instead of whatever you thought it was),you also risk prosecution and a huge fine for copyright theft.