I'm only 23, so I understand that I am young, but looking young is, without a doubt, a serious disadvantage when it comes to people trusting in your ability.

I recently worked on overhauling the reporting system for one of the largest police departments in the US, and every step along the way I was asked who was in charge, how did I enter the workforce so young, how I got an internship while attending high school (I had already graduated college), etc. I even got those types of comments from other employees at companies where I worked full-time. Of course, I don't really have the luxury of getting too offended by it all the time, otherwise I'd be really bitter, but the classic "Oh well you'll be glad you look young when you're older" gets tiring.