I think you have to look at the posters that participate often. I'd say at least 60% are older than college aged. You see alot of younger posters(my age and below) come and go so it probably puts off the appearance that its filled with young people.
Everyone in my mastermind is quite a bit older than me.
BUT Younger people do have a lot of stuff they can bring to the table. What we lack in experience we try to make up with creativity and enthusiasm