Even the people that seem dumb and slow to some are actually rather intelligent. When setting aside personal issues with some people, it's easier to say (but that's easier said than done :p). There are also people that are smart in certain areas and completely lacking in others. For instance, not every single intelligent person is toting a quick wit being that is a personality trait more than a gauge of intelligence. I've known some incredibly dumb people that still manage to have a knack with quick and witty humor and many very silent yet incredibly (almost scary) intelligence. Then you have the lazy but intelligent, wasting their gift, and so-on. Also, can't forget to count talents as being smart.

About the gammer forum age thing. You're both right and wrong. I say wrong only due to generalization, as I've met some pretty keen young people over these short years. I do still agree with you in saying that it tends to come with age, though!