A friend of mine recently had a baby with a heart condition. If she hadn't had an ultrasound they would have not known that the baby couldn't withstand the stress of labour and she would need to be booked on for a c-sect.
If she had of gone into labour and tried for a natural birth her baby would have in most likelihood died..

So yes I do believe ultrasound is needed at SOME point in the pregnancy. I don't really agree with u/s before 12 weeks as I had 3 early miscarraiges all within one week after an ultrasound, and with my DD and my current pregancy I didn't have an early ultrasound done and had no problems, I don't know if there is a connection there but I just personally would steer clear of them in the future before 12 weeks.