Spam? or not Spam? stackoverflow is a place google likes, so having a link here is attractive.
Edit to give typing instructions for URL to avoid the link?
This is a terrible user, but looking at his other questions, a legit one. I don't think the link is spam.
It will also not improve their page rank because Stack Overflow's outgoing links are
Apart from burning the question with fire because it's off-topic, I don't think any action should be taken.