My take on this is if the user gave a good quality answer and added a link to their blog without mentioning that it was their blog - no big deal. I add a comment to let them know they should add a disclaimer (just "see my blog" will do) and a link to the FAQ and hope they get the message.
The next level are people plugging their codeplex project or whatever, trying to drum up a bit of traffic. This is fine if the answer is relevant and they add a disclaimer. If not we need to let them know and point them to the FAQ. If they do it repeatedly it becomes a problem and we need to escalate.
The real pains are the people (often sock-puppets) promoting a product with no other content than "you can use xyz.com" which is a paid product - we know who they are. They hurt the site - I used to point them to the FAQ, but it's getting worse and now I'm inclined to delete them on the spot.
I think they are all worth a flag, and that's the best way of dealing with it, even the first category, because it is an opportunity to educate the users of the site.
Keep up the good work - it's appreciated.