We've had a lot of discussion about "negative SEO" in the form of toxic links, but what about negative SEO in the form of link-removal requests?
Just today, I got a link-removal request from a gmail account that purported to be from a company I've written about a few times. (The address was [companyname].linkremovals@gmail.com.) Supposedly the company had been penalized by Google and wanted to get rid of inbound links that might have caused the penalty.
I'm not about to delete a link on the strength of an e-mail from a questionable gmail account, but I'll bet a lot of site owners, bloggers, etc. are less suspicious than I am.