So what happens if you reply to a mail like this? Does the quoted part contain all that linkedin fluff?
So in addition to reading your incoming mail they can also modify your outgoing mail as well.
Suppose that user B gets mail from A, then forwards it to C. I'd see why this could be valuable info. for a company like this (and also has a high potential for abuse).
So there's a nontrivial chance that if I'm connected to someone in LinkedIn whose profile is "private", then if I forward a message from him (containing this LinkedIn flair) to some third party (who is not connected to him), then I could expose his profile details to the third party? That's a privacy lawsuit just waiting to happen.