I think I know what's going on here. I received an email identical to this one from another site "Jebet". I though it was not spam at first. I went to the site, and found no link back to my pages. As it turned out they hired an
SEO "expert", to build links. they trusted them to not do anything malicious. I can understand how this could happen. I think that as long as it's not a trend there's a little room for benefit of the doubt.
It's one of those examples of how hiring the wrong
SEO can really screw up your efforts.