Mobileedge is releasing a couple of RFID-blocking wallets in the next couple weeks aimed at the tin-foil hat set. There's a standard credit card holdin' wallet and a passport holdin' wallet, perfect for keeping prying eyes out of your least-illicit affairs. Both versions will set you back about $30 when they come out. –Adam Frucci
Uh, it's not RFID keylocks (though those can come in handy), but things like RFID credit and debit cards. Given the North American attitude towards financial institution security (passwords are good enough), once they manage to get the data off your cards (not too difficult, probably can rip off a bunch just walking past the checkout counters), well, you get the picture.
Sure, any technology can be done right, and be useful, others are technology for technology's sake (e.g., DRE voting machines, RFID passports). RFID passports being particularly nice since you can use it to identify citizens of particular countries.
Sure thieves can reach into your mailbox and steal what they need. But that's fairly complicated and can involve suspicious activity. Walking by people on an escalator or by them on the checkout lines, not so obvious.
Why do think pickpockets rely on the escalator "bump" technique? Take an ordinary action that happens so often no one thinks about it, and use the fact that no one thinks about it to profit. Like walking past a long line of people in the checkout line to exit.