What are your thoughts or experiences with age related discrimination in modern society?

It seems like teenagers are often assumed to fit a stereotype. Alternately those who are older also seem to be stereotyped.

Do these stereotypes translate to discrimination?
Have you seen or experienced age related discrimination or a gross assumption that you feel damaged your credibility?

Please note that I am not currently a student and thus I am seeking answers for my own information and not to cheat the education system.

Thanks!