Yummyham:

I have the same problem. 34 and I get pegged consistently by strangers at 24, and sometimes younger.

I occasionally have received the same treatment by employees, not to mention some very odd looks from other F class flyers (and no, I don't have nose rings, tattoos, etc., very clean cut here). I have found the best course of action is to:

1) Act your age and just blow it off (things like your card/boarding pass...just smile and show it to them...they feel silly/embarassed afterwards)

2) If employee is really out of line and/or makes reference to your age then by all means write a concise, lucid letter detailing what happened and what you would like to remedy the situation...this has worked for me.

3) Recline your seat, close your eyes, and relish in the thought that it will be ANOTHER 10 years before you look like you are "supposed" to look in the elite line or F class.

I hated it in high school and college, but I wouldn't trade it for the world now!