Apple clearly states that iPads and iPhones should not be charged from the ports on a MacBook, MacBook Air, or a MacBook Pro. Why? Because not enough current is available via those USB ports to charge them at the rate which is needed. And, it can damage the ports.
For best results, you should always charge your iPad and iPhone via the power adapter that came with them.
Are you sure? I use my MBP to charge my iOS devices all the time. Sure it takes tons longer for the iPad 2, but it still charges fine. I wouldn't think it would cause any issues other than taking longer.