How often do you test your memory? The nice thing about ECC is it's always testing your memory, and (if it's set up properly!) you'll get notified when it begins to fail. Without ECC, your memory may begin to fail, and you'll have to deal with the consequences between when it starts to fail and when you detect it.

(Of course, I don't run ECC on my personal systems, but at least I'm wandering knowingly into the abyss)