Not just their first bikes.. (in my case anyway)
Dropped my RD125LC (1st bike) in heavy traffic coming up to a roundabout, had to stop and put my foot down, my "Hi-Tec" (oh the 80's) boot laces got caught on the foot peg and I couldn't put my foot down, timberrrrr!
Dropped my RD350 powervalve (3rd bike) when trying to put it on the centre stand in the rain, boot slipped off the stand, stand flipped up, bike went over as I lost balance and me with it
And most recently.. GSXR1000 (8th bike) in France a few year ago. My mates iphone satnav was sending us in circles around Boulogne. Some temp traffic works were confusing it, so I said I'd park up top of street and wander down to see if we could cheekily ride through the dug up road. Parked bike with front wheel against the kerb (pointing down on an incline) so it wouldn't roll off the sidestand... Well that didn't work, as I swung my leg off the sidestand folded under as the bike rolled forward and went down on it's left side, with me under it
Don't think I'm ready to take my stabilizers off yet