http://gizmodo.com/5877836/why-did-t...ad-and-why-now

It says here that they did it to show off their power.

Quote Originally Posted by Molly Wood
My sources tell me the timing of the Megaupload arrests was no accident. The federal government, they say, was spoiling for a fight after the apparent defeat of SOPA/PIPA and not a little humiliation at the hands of the Web. And what better way to bolster the cause for cyber-crackdown than by pointing to a massive display of cyber-terrorism at the hands of everyone's favorite Internet boogeyman: Anonymous?