I highly doubt Apple employees are running SSN background checks on "sketchy" looking people purchasing products. In fact, another anecdotal incidence--my husband, who prides himself on looking like some wrong-side-of-the-tracks drug dealer (think long hair, tattoos, all that stuff), likes to buy Apple products using all cash. He purchased a MacBook Pro just last year and nobody asked for any identifying information, save for his email address.
Just sounds a bit romanticized to me--like when you see someone who might be a drug dealer and then you go around telling everyone you know that you, like, totally sold an iPhone to a drug dealer the other day. Yeah, right.
A few other accounts stand out as, well, exaggerated--"evil customers," for example, as well as homeless people using public computers to give live webcasts. I live across the street from an Apple store, and the hundreds of customers I've seen are polite and, frankly, boring. I'm probably the most outspoken one there, and that's because I work for PCWorld so I'm always trying to get the inside scoop (though they'll never give it to me, because they don't know and speculation will get them fired).
Gizmodo's Kat Hannaford seems to have had the same experience--it's too bad we don't live in the rougher section of town where customers go insane and drug dealers stalk the streets in search of iPhones. Though, admittedly, there are some crazy customers out there--but Apple, as I said before, doesn't have the market cornered on that.
As for the homeless-person-webcast, I'd love, love, love a link to this webcast. That would simply be awesome.
But these are just my experiences, and I want to hear yours. So, who's seen a customer go crazy? A homeless person livecast? A drug dealer get the smackdown from undercover security agents? Stories, people!