Because not dying or putting yourself in the hospital is a great skill to have.
If you happen to make bread with yeast that is old don't eat it. It's nothing I had ever really thought about before since I don't typically make bread. But I decided I wanted to make some last night for many various reasons. I've been promising my boyfriend a loaf or two, because we no longer have any (I want a damn ham sandwich) and so I could try out my mom's breadmaker. I got one of three accomplished. I used her yeast, which she later told me that she doesn't use anymore since my dad found out he has allergies to gluten and, well, you can see the results. Not pretty. And I'm still kinda pissed that I just wasted 3 cups of flour. She has said she will buy me more though, so I guess that's ok. /eta I have a crazy aunt who likes to regal us with tales of her youth and one of them deals with a loaf of bread that my great grandmother made. Apparently she had found a jar in storage that was gawd knows how many years old and didn't really think it could do much harm to use it because it was still sealed. And she had a policy of waste not, want not. Anyway, she made the bread my aunt got to it first because she loved homemade breads and ended up in the hospital the next day. And according to her, *omg I almost died.* She's still to this day convinced that it was the fault of the yeast and frankly, I'm not going to question it since it was a very basic recipie. I will however question the deathbed part since she has a flair for the dramatic side of things.