|Yep. 12 - 15 ft. is common. Some guys use longer leaders. It's kinda hard to explain, but because of the lack of weight at the end of the leader, the hook and bead(s) usually track the lead weight perfectly. Remember, the weight is set above the actual leader much like a sliding leader rig. So optimally, the weight during the cast is usually only a foot way (or so) from the rod tip. Therefore, when tossing a 15ft leader, all that hook movement is occuring 8 1/2ft above your (and everyone elses) head.
Usually, there are only 3 instances where people get in trouble.
1. Walking to close to the back of the casting line.
2. Standing at the bottom of your upstream neighbors drift. So usually, your cast will start just down stream from you. If your downstream neighbor (or you) is standing too far in front of the casting line, he's gonna get his leg caught.
3. Not letting the current provide the leader enough drift to start your cast. Letting the current hold your leader taunt prior to the cast allows the hook and bead(s) to correctly track the weight during the cast. Failure to do this will usually just cause the leader to snag in the rocks just in front of you. Occasionally, the hook snags you in the leg.
A Jerk on one end waiting for a Jerk on the other end