We've beening handling a lot of calls lately from companies who are seeing unsualy banner adds running on their websites. At an alarming rate websites running Word Press are getting hacked into through unpatched modules.
When looking through the logs it is clear that there are tons of people and companies on the internet who are trying to either hack into the sites to place ads or to post comments thater are clearly only for other peoples SEO results.
Bottom line, make sure you keep your Wedpress sites and plugins updated.
Peter Jobst