I have noticed an emerging trend for linkspammers to spam their sites on article talk pages, user pages and user talk pages, especially after failing to get their spam placed in an article itself. [[WP:SPAM]] does not have a clearly formulated policy on this from what I can see.
For instance, [[User:Hoodia]] was especially egregious today, spamming the [[Hoodia]] article, but also setting up a User talk page that consisted entirely of spam:
http://en.wikipedia.org/w/index.php?title=User_talk:Hoodia&oldid=9431556...
This case is obvious and common sense, but I have seen more subtle issues recently, such as this editor listing her site www.BreastImplantAwareness.org/ after her signature:
http://en.wikipedia.org/w/index.php?title=Talk%3AStephen_Barrett&diff=93... to bottom)
Does this count as linkspam? It struck me and other editors as inappropriate.
SEO spammers are going to want a working link from Wikipedia to improve results, so I suppose <nowiki> is an option in many of these cases. As another example, a longtime detractor of mine who was eventually blocked for linkspamming still managed to spam links removed from various articles to her bostonschoolofelectrolysis.com website via another editor's talk page:
http://en.wikipedia.org/wiki/User_talk:Alphachimp/Archive_7#PLEASE_REPLY_AND...
This is now archived and indexed on Google, effectively achieving the desired result of a direct link from Wikipedia.
These phenomena seem like something we should address before it gets much worse. I guess the most contentious one would be links to one's own sites on one's User and User:Talk pages. I'm not sure how that line should be drawn. A blanket ban would probably drive some editors away, and any policy would probably have a lot of gray area regarding what's acceptable.
Jokestress