If this is indeed not just a localized phenomenon to his local bookstore, Mark Frauenfelder introduces ‘manga aisle hobos‘ to geek lexicon. He’s still seeking alternative phrases, though. (Maybe ‘manga squatters’..? And is this only with manga readers? And do I need a separate category for ‘Manga’ on the blog because I already gave ‘Anime’ a separate category from ‘Movies’ and ‘Television’?)
Update: Suggestions are piling up at this Flickr comment thread, with ‘hobotaku’ in the lead. Any manga fans out there want to comment on this? I’m very careful to “use members’ meanings” (as we learned in my Field Methods class), meaning that I generally avoid using terms to identify people that they don’t use themselves, so I’m curious whether this would strike manga readers as simply derogatory. (The commenters in that Flickr thread certainly mean it to be.)
Geek Studies 
Well, wonderful work blocks the content of the site linked, but judging from the photo and the name, I can guess at what the term means. Interestingly enough, people have been doing this for quite some while in Japan. In fact, when I lived there, a number of stores would shrink wrap their manga (presumably to dissuade people from trying before [or without] buying)