Here is what happens. Aprox once every 2-3 days I'll be using my phone and select the "people" tile or the "me" tile. The text at the top of the screen that says something like "looking for news" stays at the top and never goes away. The people tile never updates. I can go back to the main screen and back in and it still hangs. I've noticed that when this behavior happens the phone is often very warm to the touch.
Powering off and then back on fixes the issue.
The weird thing is my data connection still works even when this still happens. Marketplace works, email works, and IE can still hit the internet.
Happened to me for the first time tonight on my L900, with both LTE and WiFi on. Speedtest showed 5.6Mbps down over WiFi, so not a connection issue. I assume its a Microsoft server or Facebook problem. Will probably clear up before tomorrow.