Visual Sciences has long been a little bit under the radar but has had fantastic technology in the analytics space. They recently hired some high profile employees including former Jupiter analyst and author of Web Analytics Demystified Eric Peterson. Peterson previously worked at WebSideStory before leaving to become an analyst with Jupiter and write his book. He also moderates the Web Analytics Discussion Group.
When Peterson took the job with Visual Sciences he noted that he felt they had the most disruptive technology in the space. This may end up being a great move for WebSideStory if they managed to snap up a company that may have become a big future competitor. It sounds as if the plan right now is to keep it as a wholly-owned subsidiary. Whether that makes sense in the long term remains to be seen, it may make more sense to combine them into one great application in the future. Congratulations to both parties.