Does age matter?

Over on A World of Snail Mail, someone posted a question about whether age matters for penpal compatibility. I've noticed while browsing penpal ads on a number of sites that people ask for penpals near their age, +/- a few years difference, no one over 50 (because they couldn't possibly write to an old person), or to young people (what would they have in common?), etc.... Personally, I have no problem with age, or even gender (another can of worms for some) for penfriendship.