I did my usual check on Taylor Bay this morning for litter and discarded prims and found an unexpected floating island. 637 m in the air was this grass lawn with a teleporter on it belonging to a complete stranger. This was not a newbie though, he's almost as old as I am and an ex mentor. Usually I just return things but I thought I'd find out if the person really thought they were going to live there.
Not a nasty encounter - just one of those odd moments that happen in SL. :)