RFID tags are big news these days, and for good reason. But I'm fairly sure that if there were any truth to this claim that RFID tags were snuck into the new $20 bills and that the RFID Tags in New US Notes Explode When You Try to Microwave Them, I'd have heard about it. Slashdot ran the story, but I still think it's not so.
In contrast, RFID tags are going to be embedded in Euros. Which I think is supremely stupid, and an invitation to high-tech targeted mugging. Plus hiding cash under the mattress won't work if the burglars have an RFID detector. No word yet on what happens when you microwave a new-model Euro.