Google was playing nice with the music/film companies and was willing to take stuff down. Megaupload was being really shifty and trying to avoid taking down content. Case in point: "When a file is uploaded to Megaupload and another file with the same hash is already found to exist, the uploader is asked if they would like to link to the already existing file. Therefore, a single file may contain multiple links to it. This has caused some controversy, since when a DMCA takedown notice is issued only the link that was provided is removed; not necessarily the file itself." and "Prosecutors claimed in the indictment that Megaupload was not DMCA compliant, and cited the example of an alleged infringer on the site known as "VV." Over six years, VV had allegedly uploaded nearly 17,000 files to Megavideo.com, resulting in more than 334 million views. According to prosecutors, although numerous takedown e-mails had been sent, none of the files had been deleted."
Basically, Megaupload was trying it's best to keep serving up pirated content by doing as little as possible in response to a takedown notice.