I agree that it's totally dependant on the people. Hubby and I got married when I was 25, and he was almost 27. We had both finished college, started our careers, and dated for 5 years. However-after our first year of dating, when I was 21, we started talking about getting married and ring shopping-and after a while, I freaked out and briefly broke up with him-I just couldn't do it at that time. A few years later-I was totally ready. Now we look back and say thank goodness we didn't do it right away!
However.....
My cousin's wife was 22 when they got married. She dropped out of juco to plan the wedding. Shocking that she never went back

Now she's squeezed out their first (of many, I'm sure) kid and that's all she's got. That kid is her whole life. No career. No degree. Nothing outside the husband and kid. Put aside the "what would you do to survive/for money/for your child if your husband was ever out of the picture" issue-but I worry about them long term as well.