[SECProto]

> Yes, weak beer will turn sour, but it takes a lot to make it harmful.

While I agree in general with what you've said, this line is wrong. Strong beer will turn sour too. Acetobacter is good up to 10-15%, it's how we get malt vinegar and wine vinegar. All it needs is ethanol, oxygen, and time.

[larsga]

Sure. Hard to get all the details into a comment that's already too long.

In general, however, strong beer keeps much longer than weak beer. However, even if it does sour, that doesn't mean it's harmful to drink.