Yes, that is just common sense, but I think I agree with Kernow on this one, if it hasn't killed me yet I will probably be OK. I also agree about the sun block, I wouldn't take risks with that.If they look weird or smell funny then you need to toss them. Or if they start to separate then you should toss them as well.
I have never used foundation in my life! However my mum adores make up she wears it all day every day and has done all her adult life. Most of that time make up didn't have use by dates and I bet if I asked her she would be totally unaware that it does now. She has never had any problems and neither has anyone else I know. I think we can get a bit over the top about safety sometimes.The thing is that with things like this, it might be the cumulative build up that is the problem. Is your life really worth using old foundation?
Just a reminder to anyone not aware, but cosmetics can become dangerous when they get older. There's some nasty bacteria that can develop.