How Real is the threat from Web based Malware?

http://www.sophos.com/security/blog/2008/03/1202.html?_log_from=rss

data from blog

1 in every 206 page requests (0.48%) were blocked as being either a medium or high risk.

1 in every 465 page requests (0.22%) were high risk.

1 in every 766 page requests (0.13%) were sites known to be hosting malware.