Facebook doesn't want to let you bring your FB friends to LinkedIn, the bastards.
Because obviously LinkedIn and Facebook are mortal enemies.
But there's a fairly easy workaround if you have a Yahoo! email account (or just make one).
Okay it's not that easy, but it does work.
First, let Yahoo mail import your Facebook contacts. That's automatic.
You would think that you could then just go to LinkedIn and import Yahoo mail contacts (which is also *supposed* to be automatic).
But LinkedIn won't "see" any Yahoo contacts that originate from Facebook unless they have been changed in some way. So what I'm saying is that, Facebook some 'cripples' the contacts in some way when sending them to Yahoo! Mail, in order to make sure they can't be "reused." By people using LinkedIn, for instance. Yeah. The Bastards.
The Workaround (s).
0) Export your Yahoo contacts list to a .csv file. Hey, wait, this doesn't work? Why? Because Yahoo has also struck a deal with Facebook to cripple the export function for any Facebook-derived contacts. So your export file will come up empty of any Facebook-originated contacts. Just in case you might be planning to bring them over to LinkedIn. Bastards.
1) Hard solution. You could just change every contact in Yahoo Email that cames from Facebook. Any small change will do. Then LinkedIn *can* see them and import them. But of course, that involves a little work.
2) Easier solution. Go to "Print" your Yahoo contacts. Use that "Print" table without actually printing it. Once it's in print form, you can get it to something usable in various ways, like converting to a PDF or table, or even just copy-pasting to Excel or a spreadsheet. Whatever.
3) Easiest, but requires a teeny bit of tech fearlessness. This dude http://campkludge.org/?q=yahoocontactexport has built a workaround.
You save the Yahoo contacts as a .html webpage.
Then download (from sourceforge) a program he made that will convert the webpage to a good old .csv file. (and then just upload it to LinkedIn, instructions below).
That worked for me.
I guess I should caution that you need to follow his directions closely. The idea of dragging and dropping a saved .html page onto an .exe is a little weird (to me) but it works, and you also have a real .csv file for *all* your Yahoo contacts, including the Facebook crippled ones.
Then you go to LinkedIn's "Add Connections" --> "Any Email" and you'll see the additional options "Upload Contacts File" and you can upload your new .csv file and just get a big list. Clink on any FB friends you want to also LinkIn with.
This sounds complicated, I know, but it worked in less than 5 mins for me. Actually the hardest part was once I had the list in front of me in LinkedIn, clicking on which FB friends I wanted to Link with anyhow, since only about half of my FB friends had LinkedIn accounts (and about half of those cared enough about LinkedIn to actually have uploaded a photo or resume).
Anyhow. This was one satisfiying way to circumvent the shitheadedness of The FaceBook.