Both Facebook and LinkedIn seem to want to make it harder to get your contacts from Facebook or LinkedIn into your own system. It keeps getting harder, and I think one day may be impossible. I STRONGLY recommend you export them all immediately, and update your list monthly if you are active on either system.
Below is a great post by Contactually on how to use their service to get the contacts merged, and if you don’t use Contactually you can export them into whatever system you use. If you don’t use Contactually, here is a link for a free 30 day trial, during which you can get your database together or if you like use it as a customer database.