I'm trying to figure out where my workmate fits in -- he ALWAYS wears sandals. (well, there was a week when he didn't last year ... we're still not sure what that was about). But in the winter, it gets cold, and he wears socks, too.
And most of the folks i've seen wearing socks w/ sandals were middle-aged tourists in the DC area. (I worked at the Pentagon for a few summers (early 90s), and more often than not, each tour group had at least one of 'em.... and about even odds on them having a kid wearing a brand new 'Hard Rock Cafe' t-shirt)