To get the names of the user’s friend, you can go two ways:
1/ make a Facebook API call on the server side using users_getinfo()
2/ let Facebook render the names in FBML using the fb:name tag and passing it the user id
While it’s tempting to speed up your application by removing the users_getinfo() call and going for solution 2/, in practice 2/ will turn out slower.
You won’t notice the difference when the users doesn’t have a lot of friends, and in this case 2/ may be faster.
But past 200 friends, and 2/ is extremely slow.
An extra goodie with 1/ is that you also get access to the friends names on the server side, so you can do more processing.