1: Spam backlinks are bad for seo
2: It makes webmasters angry
3: The backlinks let the webmasters who you just made angry know what your website is.
So the point of this post is basically a call to arms for all warriors. When you have a bad day or if a comment really makes you angry then take it out on the spammers. Go to their website and write anonymous abuse in their contact form telling them how you're going to backlink blast them with 100,000 backlinks in 1 day for spamming your blog. Tell them they will be deindexed from Google after you blast them. Be creative! There are thousands of ways to scare the living crap out of them! Basically make them poop in their little panties with fear and then let us know what you did in this thread. Make sure not to give away who you are to the spammer though, you don't want to compromise your website. Also ONLY go for the worst offenders who really take the piss with their comment spam.
Here is my spammer payback story: Some douche decided to spam 10 comments on my website for his crap product. I went to his website and it had auto approve comments as well as a comment feed on the side of the page that displayed the comments on EVERY PAGE ON HIS WEBSITE! What a complete moron he was. I then proceeded to write a comment that said "Do not buy from this man. He comment spammed my website and will probably steal your money because he is a spammer" on the next line I pasted in 20 links to adult websites (I hear google likes adult links lulz). I then proceed to copy, paste and repost it onto 30 pages on his website (a rule of thumb for revenge is to give it back 3 fold) these comments then showed up on every page of his site too (including the home page) because of the comment feed. Hopefully he learned his lesson and decided to respect other webmasters.