Thanks for all the great feedback folks!!
We will consider the damage deposit for all since I now understand how it works.
As for the bad guest M.O., we are in a high tourist area so we don't have many locals, and I can't really say there is any commonality for the abusers. Maybe younger (under 30), groups of friends more likely than couples, and event attenders e.g. attending a wedding. But then again we've had some 18 year old guests that have been among the best...
I think we have only had one problem guest that had multiple reviews. All our other bad apples have been zero review guests. For what it's worth.
Thanks again everyone!!