Facebook App on iPhone has a very useful function to sync your Facebook friend pics to your iPhone contacts. When you receive a call from your Facebook friend, you will immediately find out who’s calling by seeing the exact same pictures of their Facebook profile pics as you see them everyday on the news feed.
You must send your personal information to the Facebook in order to match your contacts and Facebook. You should be careful with your privacy stuff.
The following screen shots are captured as on March 30, 2012
1. Launch the Facebook iPhone app & tap the menu button on the top left corner
2. Tap “Friends”
3. Tap “option” button which is “arrow” icon on the top right
4. Tap “Sync Contacts”
5. Tap “Syncing” to turn on the sync
6. Read the caution message and tap “Sync Contacts”
Then, the syncing process starts. Depends on the Internet speed and how many friends do you have, it would take from seconds to ten minutes … maybe more.
Good luck.