Beer doesn't go "bad" unless your sanitization is weak. Since nothing PATHOGENIC can exist in beer/wine/cider/mead, there should never be a reason to ever fear tasting something like this, no matter how old it is. Yeah, it may taste like crap, it may be vinegar, but NOTHING that could happen, could ever cause harm to anyone.
It's not worth passing by on something that could be amazing, because of fear.....
Noone thinks twice about drinking old wine.....
Homebrew is no different from commercial beer. Properly stored it can last and be drinkable for 100s of years.
To put it in perspective, in the Dec 07 Zymurgy Charlie Papazian reviewed bottles of homebrew going back to the first AHC competition that he had stored, and none of them went bad, some had not held up but most of them he felt were awesome...We're talking over 20 years worth of beers.
This is a great thread about one of our guys tasting 4-5 years of his stored brew.
And I brewed an og 1.150, 150 IBU barleywine that I won't be opening for 5 years.
Not to mention the fact that there are vertical tasting for certain beers like Stone epic, where people collect each years beer and then sample a flight of them going back in time.
I just had this expericence not too long ago... We tried 48 year old beer today.
One was interesting and drinkable, and one was gnarly.
Mbowenze has a thread about tasting an over 100 year old beer recently. And In my history thread there's a video of the OZ and James Drink to Britain tv series where they taste a beer older than that.....one that goes back to Napoleanic times iirc.
It all depends on how they were stored.