The act of exploring deep web page links, usually irresistable.
Typically starts out as a link sent by a friend or relative ("hey look at this!"), then an interesting link catches your eye. A couple hours later, you've traversed the bowels of cracked, holytaco, thechive, reddit but not digg because nobody goes there anymore, and a dozen other news and link aggregator sites. More often than not, this will happen at work.
Sorry, boss. Didn't mean to waste four hours on that spelink today instead of doing your TPS report.