Those people it's suggesting have probably e-mailed you in the past, or are in the networks of people that have e-mailed you in the past. LinkedIn matched your

Those people it's suggesting have probably e-mailed you in the past, or are in the networks of people that have e-mailed you in the past. LinkedIn matched your e-mail to their address books, which they gave to LI when they let it connect to their Google/Yahoo/etc mail accounts in the past. If you sign up with a fresh e-mail address nobody's ever seen, you'd have no initial recommended connections.