I've never been ashamed of my age - I quite happily joke that I am the old lady of most groups I am a part of, especially mothers of children the same ages as mine because I am considered an older Mum to my nearly 12yo and an absolute dinosaur Mum to my 13mo!
I get on with people of all ages and to be honest, i don't look at someone and try to guess how old they are before I decide that I may or may not get on with them - I talk to them, get to know them and then decide!
btw ... for those who are curious, it is common knowledge that I am 43. Not so common knowledge that my gorgeous DH is 35
I think, however, that it has been a long standing taboo to ask another person's age. I certainly remember being told not to be so rude when asking a friend of my mother's how old she was when I was a child. One of my grandmothers never disclosed her age and my grandfather certainly didn't. When he married for the second time, it wasn't until his new wife signed the marriage certificate that she found out that he was in actual fact, 17 years older than her. She had just assumed, because he was so fit and healthy that they were around the same age.