Font license scam? Wondering how common this is.

Recently got an email from "Paratype" that one of my sites was using a font that was unlicensed and we needed to pay a fee. I inherited the site from someone else so had no idea about the font, which was hidden in a Bootstrap library, so the decision was made to remove it completely. I replied to Paratype stating this and they replied, "Well, you were using it in the past, so you should pay us anyway." Obviously I'm going to tell them to piss off, but I was wondering how common this sort of thing is? I doubt they have much of a claim legally, the wording of the email is pretty weak sounding to me. submitted by /u/TConner42 [link] [留言]