It is possible the ECU is bad, and I've had it suggested before. However, being an electrical engineer, I find it very unlikely that an ECU would just "go bad". They should be one of if not the most dependable electronic component on the car. I would be inclined to suspect many other parts before giving in and replacing the ECU as a last resort. In my case, I don't have any strange codes to suggest it, just strange operating characteristics.
All that said, strange things happen and it very well could be the ECU.
Mine: 2002 Focus SVT: 142k, Sonic Blue, #1654, All Options
Mods: Tom's Tune, Borla, HFC, STS, Painted Machs, Euro Grill, FRPP Springs
Hers: 2010 Focus SES: 67k, Ebony, Auto, Moon and Tune