If you don't offer your users the option of creating a "local" account, I can guarantee you I won't be using it. LinkedIn is horribly invasive if you don't put it in a very strong cage.
Now linked in is asking me to invite people to join LinkedIn, who are not yet members. I assume these "leads" also come from contact lists sucked up by their app.
I was asked to invite a mailing list to join. I belong to a private mailing list, which has a name. I assume that list's address was sucked up by the app.
To the people at LinkedIn who implement this stuff and enable this kind of behavior, faking communication from people who did not actually inititate it: Really? That's what you do for a living?