No I would never jerk someone around like that either, and I sure hope nobody else on these boards would seriously consider it. But the way the question was stated sounded sort of like a logic puzzle, so I couldn't resist exploring all the possibilities.

If I were the leader of the big group, I would know in advance that I would have trouble finding big campsites. So I would either stick to big lakes with lots of alternatives or get up very early and make camp early too.

If someone gets to a site before me, it's theirs, period. If it's 1 pm and my prize site is already taken by a solo canoeist, well there are worse things in life than a little extra paddling in Q, aren't there? (ie your hypothetical whiny group member may need some attitude adjustment, but Q is a good place for that)

On the question of etiquette: shouldn't all groups on nonisolated sites try to be as quiet and unobtrusive as possible, regardless of whether the other site is occupied by Greta Garbo or another pack of schmeauxs? Whether the solo paddler wants to be alone, or just wants to paddle alone, or is alone due to other circumstances should have nothing to do with it.