Ahh, this brings back memories of all those pointless debates in school.
I don't think age has anything to do with it, i know 16 year olds who are well versed in politics and 40 year olds who are complete idiots, read papers just for the gossip and have no interest or knowledge of politics at all.
Once you become legally old enough to be considered responsible for your own actions then you deserve a right to have a say in how your country is governed. Of course, these days prosecutors seem willing to try younger and younger people as adults (and you could argue that kids grow up a lot faster these days), so if anything the age limit should be reduced. But i think 17 - 18 is about right.
Voter inteligence is a totally different matter. I guess we could test people to see if they know enough to vote
Unfortunately there is no way around the fact that 80% of people who do vote will probably know almost nothing about any of the issues and be voting based on how they were brought up or the views of whatever media they are exposed to.
Voter apathy however is something that they might be anle to do something about. Howard Dean, whatever you thought of him, did manage to connect witha whole section of the population that rarely votes. Internet and other high tech voting methods are definately a step in the right direction. I'm also highly in favour of including a "none of the above" option on ballot papers, as i often feel none of the candidates are suitable, but my only option then is to note vote at all. I'm also all for fixed spending, free advertising slots and anything else to try and take the "buy your way in" feeling away.
But i don't think age has anything to do with it at all.
What i do think needs to be addressed is breaking up the old boy network that all politicians come from and possibly introducing some younger politicians. I'm not entirely sure how you would accomplish this, but I think part of the reason young people (and other groups) don't care about politics is that they don't feel represented. For a 2 chamber system maybe the second chamber should be "fixed" somehow to proportionally represent the population, or to allow "non career politicians" to sit for short terms. I don't know. I do think something needs to be done though.