iirc when you sign up, they sua sponte take all your contacts from [fb, Google, your phone, etc] and message all of them saying you have invited them to join LinkedIn. This is the scummy behavior I assume the poster is talking about.
I signed up with a fake name and throwaway email the other day and I couldn't believe the process. There were about 8 steps for entering more and more personal information and one of them was definitely allowing linked in access to my email account.
