Then your form doesn't really allow for that. You're only asking to list the coolest thing someone has built. Why not change the form to: List the coolest thing you have built (maximum of three).
This enables the 30+ year crows to show their broader list of accomplishments and not artificially tilt it toward the younger audience.
You say you have higher standards but then you don't allow the higher standard to show. What if someone has consistently hit singles (to use a baseball metaphor) and a rookie has one home run. You're rewarding the onetime home run over consistent delivery. I'm not saying one is better than the other, but you need diversity and your system discriminates against that.
Hey, this is your show and you're going to run it the way it fits your need. However, with risk of blacklisting my name, I feel it's important for someone to speak out and help you see it from another perspective.
You also wrote this [1] back in 2007. Have your views changed since then?
Edit: As mentioned in a sibling comment, This appears to be an issue with Safari where items 'below the fold' don't render. Strange.
There's more value in educating and pumping enthusiasm into a 16 year old than a 65 year old.
What happens to these 16 year olds when they get to be 30, 40, 50. Do they think they are no longer able to start new things or they are less valuable? Because this is the message we are sending.
Nobody is saying you can't start new things. I'm saying the game is creating new experiences on hardware that didn't exist a year ago for, usually, a demographic of people under 30. Trying to break into that world as a nobody outside of that demographic and life experience is a long shot. Not impossible, but energies are better spent fueling people who have an actual chance at changing the world (and an entire lifetime ahead of them to do it).
Edit: to clarify, I think you incorrectly assume they're asking for age to filter for candidates that are younger. I don't think they use to filter at all, but even if they do, I would consider it highly improbable that it is to target a specific range.