Pornographic terms represent 25% of all internet searches

Various statistics on this page including:

"Pornographic websites	4.2 million (12% of total websites)
Pornographic pages	420 million
Daily pornographic search engine requests	68 million (25% of total search engine requests)
Daily pornographic emails	2.5 billion (8% of total emails)
Internet users who view porn	42.7%
Received unwanted exposure to sexual material	34%
Average daily pornographic emails/user	4.5 per Internet user
Monthly Pornographic downloads (Peer-to-peer)	1.5 billion (35% of all downloads)

Source: Various, cited by TopTenReviews, 2006