Linkedin are just a bunch of spammers anyway.
I got an email from them, claiming that someone I knew wanted me to join. It was a spammer - the "custom message" that was included was a single link to a spam site in China.
The email had a "if this is spam..." report button, so I used it, and noted to linkedin that I didn't know the person, and it was *obviously* spam (the link was to a spam site.) Their automated system thanked me for reporting the abuse, and I thought that was the end of it.
Two weeks later, I receive a "helpful reminder" from Linkedin, telling me that I hadn't confirmed or rejected the invitation. Not only had they not taken any action, they helpfully included the spam link, and seemed blissfully unaware that I had reported this spammer's account two weeks prior.
Linkedin are just a bunch of scummy spammers. I blocked all email from their domain since.