I had to spend around three weeks in Marathon a few years back, when there was still plenty of anchoring room and not so many moorings. It was much more pleasant then, and it was the best place in the Keys to get stuff done on your boat, but I agree that to me there isn't enough there to interest me as a cruiser for more than a few days at the most. Nowadays they've raised the price on the dinghy dock to $22 per day, which means I won't be going there anytime soon. And to your other point about the herd instinct--it is rampant everywhere. You can find nice spots almost anywhere that are not popular anchorages because "nobody anchors there." If there isn't a little anchor drawn on the chart or in the guidebook, or there isn't a listing for it on some online guide, nobody anchors there. I must admit that I am one of the people that is drawing in the little anchors in the books too! It can be rather funny, if you've had a cocktail or two, to be the first boat to drop the hook someplace like on the Bahama Banks near where the old Russell Beacon used to be and pretty soon you'll have a little group of anchored boats all clustered around you, despite the fact there is infinite anchoring room all around.