A report from security firm MarkMonitor states that 43 sites identified for piracy attract 146 million visits daily for a total of 53.29 billion a year.  67% of those 43 sites are hosted in North America or Western Europe and according to the study the 3 largest - RapidShare, MegaVideo and MegaUpload - collectively get 21 billion visits each year.

To be sure, some of the named sites also host legal content and a only fraction of the unauthorized content is music, but these stats are sure to fuel those call for tougher crackdowns.

More: How Artists Can Profit From File Sharing (MusicThinkTank)

Readers: Do these stats surprise you or change your opinion of efforts to stop unauthorized downloading?