Hi Mahlon,
It turns out that when a user signs up for a LinkedIn account, their profile URL is automatically generated in the format http://www.linkedin.com/pub/name/n/nnn/nnn. Users then have the option of creating a more meaningful URL in the format http://www.linkedin.com/in/username, specifying an available username as they see fit.
It looks like currently, our LinkedIn field is set up take the custom username that LinkedIn users can obtain and navigate to their profile based on that. It also seems to handle full URLs for user profiles with a custom username, with the exception of the http:// bit (so www.linkedin.com/in/username will also work, for example). It doesn't seem that it's set up to handle the old /pub/ URLs.
I'll put a feature request in for this and keep you updated through this thread.
- Justin