Unfortunately, the web is becoming a much more dangerous place as 0.1% of the entire internet is malicious. Moreover, there are no safe neighborhoods… Even sites like Al Gore’s An Inconvenient Truth and the Miami Dolphins have been attacked in the past.
Even the MySpace profile of Alicia Keys has been used to spread malicious code.
Hackers have gotten quite good at ferreting out unprotected pages and subsequently loading these pages with their "evil-doing" programs.
A few months back TMC was bombarded by hackers looking to insert malicious code into pages via SQL injection in fact.
Website owners have to be vigilant and always on alert to such practices by hackers who are constantly evolving.
Of course some webmasters aren’t and this is the problem for users.