Any one vote could swing an election, people's lives and livelihoods are on the ballot paper. Call me a centrist but I wouldn't be too happy if my bus driver was a sixteen year old or my dentist was a sevteen year old. Sure you might have the odd gifted young driver but am I going to let that determine the rules of the road, not a chance.
Young people are more likely to be easily influenced by topical issues without considering economic implications, the vast majority of teenagers will have no concern for what's done with the adults tax money and they will make impulsive decisions based on some fad they've picked up at the latest Twilight convention.
Rugrats who've recently graduated from creche voting in the next minister for video games and theme parks is no way to run a country.
The biggest worry with lowering the voting age is that the majority of kids will look to one or two sources for guidance and you'll end up with larger votes for the established parties, locking people into voting habits from a younger age without them ever exploring or developing individual political beliefs.
While we shouldn't discourage young people from considering politics and/or political activism, I think we should also avoid confusing enthusiasm and responsibility. While a small portion of younglings are politically atune the vast majority are still trading pokemon cards and completely a bliss to the world around them. If I was to give any 16 year looking for a voting card some advice, I'd say you just need to continue growing up, you're nearly there. In the mean time try get involved with local campaigns and work on developing political views through existing organisations.