My thought was more along the lines of preventing any spam here being of any use elsewhere.
I know Google USED to base pagerank on how many links a 'site had leading in. I understand they did some revision because spammers were flooding links into unrelated 'sites. I don't know why these jerks are doing this, as this audience is both small, and unlikely to be interested in the services/goods they're peddling. This leads me to remember the old pagerank schemes. Robots.txt wouldn't be for them. It'd be for Google, Yahoo, and the others.
And now they're creating new threads to spam with.
I say it's time to sweep them up, flush them, and institute an invite-only to post in the regular threads policy. This has worked okay for the Gingery group over on Yahoo. You have to send an email to one of the admins to get in.
I'd prefer something like the rating system I've seen on other sites, (I thought it was digg, but evidently not,) where other users can thumb up/down a comment, and too many negative marks will "bury" it. Used more to bury trolls, but should work for this. I just fear it'd be too much work in setting up. It'd still need policing to keep "silent partners" from upping the ratings on these things.
A truly sophisticated system would allow multiple groups to be identified and kept separate. If you NEVER agree with the "silent partners" of another, the aggregate scores of posts that you saw wouldn't take their marks into account.
Maybe someday. Probably soon.