It is fact. http://news.cnet.com/2100-1029-6140191.html
Law enforcement absolutely has that capability, as well as turning your phone into a tracking beacon even when it's powered off.
See here for more info and discussion: https://news.ycombinator.com/item?id=6722519
So your reply is somewhat disconcerting, because it seems to indicate that you think the claims are bogus. And if you think so, then you have good reason to feel that way, since almost all of your views are, well, reasonable. (An aside: would you please write something articulating your deep hatred for Soylent? It was shocking to discover you felt that way, and that I didn't see anything wrong with Soylent, so I've been silently hoping to someday see a writeup from you in order that I may find reasons to change my own view.)
In short, I accepted long ago that there's roughly zero chance of going through life without unintentionally believing in crazy things. Everyone does, at some point. Therefore the most important thing is to keep my eyes open for evidence of my own crazy beliefs, so that I can constantly reevaluate them.
So your reply seems to be strong evidence that someone I respect thinks I'm being a bit bogus regarding cell phone tracking. If that's the case, then I'd love to hear your thoughts on the subject so that I can revise my own.
Now, in most devices these days you can't be sure "Off" is actually "Off." I bet many Android phones lie about "turning off" and just go into a low-power-with-quick-reboot sleep mode.
If you successfully redefine Off to be Maybe Off, nobody can argue with you because you changed the terms of reality.
The claim isn't my own; it's Trevor's, the founder of Anybots, and one of the best electronics hackers in the world. https://news.ycombinator.com/item?id=6087399
He seems to have a pretty good grasp of reality, and he's more intimately familiar with the electronics than most of us.
I also presented some circumstantial evidence indicating that law enforcement does in fact use this capability in practice, the last time this came up: https://news.ycombinator.com/item?id=6722519
If there's fault with this, then I'd like to understand why.
The first bit that approaches being evidence is the CNet article linked from the link, and it says
Details of how the Nextel bugs worked are sketchy. Court documents, including an affidavit (p1) and (p2) prepared by Assistant U.S. Attorney Jonathan Kolodner in September 2003, refer to them as a "listening device placed in the cellular telephone." That phrase could refer to software or hardware.
So the absolute proof is a court document that doesn't provide any details about the mechanism used to compromise a dumb phone in 2003.
The "capability in practice" you link to is slightly questionable because we have A Dumb Bad Guy claiming they turned their phone off. We don't know the entire story.
Regardless of everything here: you are right that phones are out of our control at this point. If you don't want to be found, don't keep anything capable of emitting RF around you (including, but not limited to: phones, laptops, tablets, anything with RFID/NFC embedded, toll collecting car passes, tires with embedded RF transmitters for authentication or tire pressure checks, bluetooth headsets, bluetooth speakers, wifi/bluetooth digital scales, bluetooth hearing aids, ...).
I don't have a deep-seated hatred of Soylent, but it is clearly not my favorite YC startup. It's aesthetically incompatible with me, but I think there are valid scientific concerns about the approach as well.
That discussion goes into the definitions of "off" as they apply here, and Matt Blaze acknowledges (circuitously) that what we think of as "off" could conceivably leave the radio powered.
BTW, there are recent news about FBI secretly activating webcams: https://twitter.com/tinyrevolution/status/409311691088723968...
If you pause and think about it, cell phones don't have in-series recording lights on either front or rear or side or underside cameras.
Few people think "cell phone out" = "camera on" unless somebody is holding the phone "as a camera." It's easy to hack how you hold a phone to get around that.
Legislation is written and enforced by the government, and they're the ones we're trying to stop. I doubt you'll see this approach work.
Imagine if every laptop & phone (and now, television) had one of these?
Heck, right now I have countless electronic eyes staring at me ... television, laptop, phones that happen to be in the room. Can I be sure that nobody's watching me remotely? Hell no.
The NSA passes the FBI a tip. The FBI needs to get this tip admitted into evidence, so they claim they overheard it on the phone. One snag: the target's cell phone was turned off when the conversation took place. Solution: a magic bug that can listen even when it's turned off.