Do people with better memories store more information in their brains? Maybe not. Last month a cognitive neuroscientist (Edward Vogel at the University of Oregon) published a paper in Nature showing that certain types of memory capacity may have less to do with how much raw data you can store than with how selective you are at letting in relevant information. (Here's a press release describing the experiment.)
Notably, Vogel describes the brain filter that keeps the bad stuff out as a nightclub bouncer. Regrettably, I think my brain hires bouncers from a temp service. Sometimes I get the "come one, come all" circus caller who will let in hobos, Hiltons, and stray cats ("Hey look at that piece of lint! Oh, wow, tin foil!") and sometimes I get the off-duty SWAT team member ("I'm sorry, did you just say something?").