What would you nominate?
I'll start the ball rolling: I think we need a banned-content plugin. Regular expressions (e.g. "cheap-viagra-levitra.com") could be added to a list. This list would be checked against edit text before the node is written. If a match is found, an "Edit Denied" error is shown. Optionally: the IP address is also added to a banned IPs list that are not permitted to edit. It would be fairly trivial to set up something that gets the big list of http://www.communitywiki.org/cw/BannedContent on a nightly basis.
The need for this is clear, IMHO, given that OpenGuides sites are being subjected to a barrage of spam at the moment which comes from a range of different IPs every time - simple IP blocking will not defend us against this.
Thoughts? Other suggestions?