2009 was the year of malware attacks that use stolen FTP credentials to infect legitimate web sites. Hundreds of thousands websites have been hacked this way and suffered from hidden iframe injections, Gumblar, redirections to bogus anti-virus sites, etc.
The success of those attacks is based on the fact that a significant percentage of web surfer are webmasters and site owners themselves. Once a computer of a site owner is infected, malware can steal his/her FTP credentials and use them to make the site distribute malware to unsuspecting visitors, who, in turn, may also be site owners. As a result, we see rapid growth in number of compromised websites.