I've got the same problem. It can lead to problems all up your body, the flat feet turn your knee's in, which puts pressure on your hamstrings, which tightens your lower back and so on up to the neck.
However,if you keep flexible you should avoid most of the problems.
Always good to go and speak to a specialist though, they do some good insoles which can stop most of the problems.
I had alot of trouble when I was still growing because of my flat feet but nothing for a while now, I do wear arch support things for my work shoes but not in my trainers.
hope that helps - go and see a specialist if you get any leg, foot or back pain though.