I know that Comodo has a mixed reputation in this forum, and I'd like to add to the mix.
Short answer: they appear to be scanning for HTTPS servers, snarfing down the SSL cert info, and contacting customers who certs are nearing expiry in an attempt to get the SSL cert business.
A customer got one of these, and I was able to head it off at the pass, and wrote up a blog post about it. »blog.unixwiz.net/2013/03 ··· biz.html
Anybody else gotten one of these calls?