Oh yes -- people tend to underestimate my age and experience level all the time.
A few weeks ago, DH and I were at a bookstore. My club card was set to renew, and the guy at the counter said if it was my mom's card, he'd just let it slide. I said, no, it's my card. He got all flustered and said, "It's not like I mean you're too young to have your own card ..."
I REALLY wanted to ask him just how old he thought I was!! Cause it really seemed like he thought I was in high school. Even when we left the store DH said, "I think he thought you were a teenager!"