They just said on the national news that a fan blade is missing and another one is damaged. That explains the engine shaking (imbalanced compressor)...
Interesting to note that the engines are mounted on shear bolts and are designed to break off under heavy vibration rather than damage the wing/airframe - watch out below!
The USAF lost an E-11A communications relay plane in Afghanistan in 01/20. One of the engines came apart due to turbine blade failure and the pilots didn't know which engine blew, so they shut both of them down and ran out of altitude before they figured it out what to do, both died and most of the plane burned.
Some years ago a KAL plane landed at one of the major airports in Germany. During the routine ground inspection, they found a cracked fan blade...wired together. I guess the SHTF over that. I'll bet the crew didn't know what they were flying.
A coworker/close friend of mine had family on that flight - his sister along with her husband and 3 children. I just watched the video of her CNN interview earlier this evening - pretty crazy. Story I heard was a vane broke and caused the failure...