Some hardcore porn sites are already exploiting an unpatched security hole in Internet Explorer's Vector Markup Language (VML). For details and news of fixes, see Microsoft admits to IE vulnerability being expoited on porn sites on the Ask Jack blog.
Of course, what's on porn sites now could quickly be used by other risky sites, including ones offering free MP3 files, games, and so on.
As Microsoft explains, one workaround is to unregister the VML code. As I point out, another is to use a different browser, such as Firefox or Opera.