encyclo - 6:51 pm on May 28, 2010 (gmt 0)
Use cloaking to hide outbound links entirely from search engines
Just to make things clear, the spam problem is NOT about links - spam is much more than pagerank. It's about promoting directly to a targetted audience - WebmasterWorld members - which can just as easily be done with cloaked links or no links at all. See the Professional Forum Spammers thread Brett linked to above - it's happening day after day here at WebmasterWorld.
Swatting link-drops is easy - I banned thousands of such spammers when I was admin, it's a big problem but easy to spot and handle by the mod team. The real issue is the much more sophisticated and insidious spam.
<added> all outbound links are already "cloaked" (passed through a redirect script) in the forums, and have been for years. </added>