In fact, I just saw a kid with an ultra low seat this morning.
Heck, even the President's seat is too low.
I think this is the most common issue I see in novice cyclists. It may not seem like a big deal, but you really can jack up your knees and back riding this way. Plus, it is just really uncomfortable. Not to mention, riding your bike this way takes a lot more effort. You may even be better off walking.
The good news is this is a really simple fix. Even a mechanical and tool dummy like me can raise a seat. This is saying something since the extent of my tool knowledge essentially stops at flat vs. Phillips.
If you are a novice cyclist and don't want to do it yourself, stop at your local bike shop and just ask someone working there. Chances are they'll give you some good seat height advice and probably raise it up for you (for free) if need be.
If you are a novice cyclist and you do want to do it yourself, here is some good advice:
If you are looking to ride more seriously and are riding clipped in, you may want to consider a professional bike fit. It is definitely worth it.
And, if you are looking to ride more seriously but don't want to pay for a professional bike fit (yet), here is a more detailed DIY tutorial.
So basically, if you feel like this when you're riding your bike......
.....raise your seat!!