As the internet hits its 16th year the user demographic will probably be slowly heading towards a more normalized curve (though I'd expect to see the peak certainly biased back towards the younger age groups at least until they discover some cool new medium and leave us old folks pioneers behind)
With that in mind I was very amused to see the error message when I was customizing my profile for the new Windows Live SkyDrive service. The minimum age of 18 tied in with the terms and conditions, but... an upper limit of 255! What do they know about the target demographic for Live services that I've not been told about yet!