I'm having something similar to Decius' inexplicable Twitter lockout experience a while back. Signed up for LinkedIn a couple of days ago. I've been diligently building out my network like they encourage you to do. I signed in this morning and I got this:

Account Restricted | LinkedIn

Your LinkedIn account has been temporarily restricted

Contact our customer service team to get this resolved as soon as possible.

Clicking the link to the "customer service team" takes you to a generic form that asks for your name and email address. It auto-populates the subject line with "Account High Restricted" and the form says "Your Question"

When you submit you get:

Your question has been submitted to LinkedIn

The ticket reference number for your question is: #

You've successfully submitted your question, and we'll send you a confirmation email soon.

Go to your Support History page to check out your ticket.

What's really funny is when you click the link for "Support History" it loops you back to "Your LinkedIn account has been temporarily restricted.

I love mediated online social mechanisms with arbitrary kill switches!