How often does an ECU write a car off?

[crofty1984]

I mean, I know they can be expensive compared to the price of an old car, but how often do they (not the MAF, not the injectors, the actual ECU) actually break, rendering the car inoperable?
I remember a lot of "oohhhh, it'll break, at least you can fix carbs and a whirlygig with a half brick and peice of string to get you 'ome!" - I say that as a guy who's most modern vehicle is from the mid-90's and runs on carbs, so no hate here.

Just saw a similar comment in the Defender thread along the lines of "all those ECUs going wrong!"