Ah, the memories.

This entry from Bookgasm's 9 Most Annoying People I Always See at the Bookstore list brought it all back:

AISLE SITTERS
I’d love to look at those books on that shelf right there, but you’re sitting in front of it, your back leaning against it, reading material in your hand, making yourself perfectly comfortable. Odds are, your coat and purse/backpack and whatever else you can litter about your person are.

There are a few more I'd add, like the people who wander around leaving (as my friend Sean put it) "viscous fart clouds" among the stacks, and, my least favorite -- the people who, when they find an item that either doesn't have a price sticker or won't ring up, say, "Oh, well it must be free, then!"  (Both of those get mentions in the comments section, so I'm happy to see that I'm not alone there!)

(link via Quillblog)