Scraping Booth Barnacles
Yes, I coined the term in 2002. Consider it my linguistic gift to webcomics.
Booth Barnacle (barnaclous blahblahblahblus): A fan who stands in front of your booth for way too long. Sometimes they've bought some merchandise, and sometimes they won't buy a thing. Sometimes they're talking incessantly, and other times they're just... standing there. But they're making it impossible for you to do what you came to the convention to do.
I know what you're thinking: Clearly, these are the wizened musings of an aging comics curmudgeon. The poor, old fellow has had one too many exhibitor badges slung around his veiny neck, and he's finally hardened to the loving fan interaction that once brought him to webcomics.
First of all... ouch.