Just having a good bit of fun today. We're letting spammers help us rank on the search engines.
Now, one of the key points search engines rank you on - apparently the hardest one to get for new blogs - is popularity, particularly this point of other people leaving comments on your blogs.
I used to shut them off. Recently, I installed b2evolution on a couple of different places - and they have some interesting weaknesses with trackback spam, among others. But you can also use this to your advantage.
Some years ago, I noted that you could edit these spammers and have them link back to some other site, another of your other sites, or even to another page inside your own blog/site. All of that is fairly legit. Of course, you would want to change their content so it's actually applicable (some attaboys are permissable...). If you got really creative, you could even sestart a conversation between those scammers and have them answer one another.
The advantage of editing their work is that every time they scam you, they leave (pretty much) a unique IP - which you could otherwise simply post comments to your own blog, but sooner or later, the search engines would figure this out.
So since you have to go to the hassle of working with that spam (such as deleting it), why not simply put them to work for you and help you with your own SERPs?
We'll see how it pans out, but it's not costing me much at present.
(And of course, if a particular spammer gets too annoying, you can just ban the IP via your site control panel...)
Have fun with this...