I'm actually super curious about that too, as far as I know pathogens cant live in beer, so I don't know how it can go bad.
I wonder though if local brewery's or more artigianale brewing processes are different and maybe could be a bit riskier ?
I wonder though if local brewery's or more artigianale brewing processes are different and maybe could be a bit riskier ?
Brettanomyces will make your beer taste phenolic. Lactic Acid Bacteria will sour it (Lactobacillus and Pediococcus are two common contaminants).
Oxygenation will gradually make the beer taste like cardboard.
Hop aromatics degrade rapidly, heavily hopped beers are best within a month of brewing.
Very few beers get better over time (generally sours and stouts), most are beginning to degrade immediately and fall off a cliff within a year.
Also as you probably already know brett, lacto and pedio are desirable sometimes.
Depending on the beer there might be live yeasts in it.
Beers can still go bad. Not always from a "not safe to consume" but often at least a "not going to taste very good anymore" kind of thing. Beers will end up oxidizing, the stuff in the beer will degrade over time, etc. Not all beers age well, some need to be had within a certain period of freshness.
Generally I prefer a "born-on" date for beer.
The flavor going off is the main concern with beer.