The government

 

If you’re a U.S. citizen and you’ve gotten a new passport in the last few years, guess what? There’s an RFID chip in there. That alone isn’t a big deal, since the passport itself is a method of tracking your movements. Government agents sit in airports all over the country, carefully logging the visas stamped in passports, asking invasive questions, and being generally nosy.

Now they don’t need an actual physical presence to track you, and the capability to do so doesn’t end when you’re out of the visual range of the dude in the bulletproof booth. The tag inside your passport has a broadcast range of a little over thirty feet. The first batch of tagged passports included no shielding and no encryption. More recently, the government’s added a thin metal sheet to the cover of the passport and weak encryption to the chip itself, but the effectiveness of these measures has yet to be established.