In reply to boothy:
Pre-clipping the first bolt or maybe two is really done to stop the climber decking in situations where the start of a climb can be particularly sketchy or awkward.
If you see someone doing this outside then you'll see that them getting to the first clip or so is a bit/very hairy, and the likely hood of them coming off in an uncontrolled way (from say a heel-hook, dyno etc), into say a pile of boulders, elicits the application of a bit of common sense. No route is worth crippling yourself over.
If you see someone cruising up past the first couple of pre-clipped bolts, then they may well be being a bit of a nob, and are trying to save their energy to claim the Lead. If you see this scenario happening indoors, then it's a combination of the above ego, and bad route setting.
Of course if you see the climber has a bad ankle, then the previous statement about common sense might well be more accurate.