I'm twenty-three and have been active in the poly community for a year and a half. I don't feel marginalised because of my age. I don't feel threatened by older polys. I know what's healthy for me and what's problematic. If I did not know those things, I would not feel fit to date anyone, much less poly folks.
I appreciate redpepper's concerns for my safety, but I have felt more pressure coming from people my age regarding the things I do with my body. CdM has respected my boundaries from the start, unlike the twentysomethings I have dated. I would put a lot of younger people's vulnerability down to a lack of self-knowledge, and I made sure I learned before I went out and gave it a go.
I don't really see age when I make friends. I find that the human experience isn't so different across generations, and where it does differ, we are better off learning from each other than closing our eyes. If you're legally an adult, I like you better if you behave like one. Mostly, I think in terms of interests, and my interests happen to span different age groups.
Incidentally, I know of veterans and parents who went to school with me. My generation is at war, too. My generation can get pregnant just like any other.
I realise I am something of an anomaly, but I'm a happy anomaly, drat it.