Kevin Mitnick figured out how to get around police radio encryption in the 90's. From 'Ghost in the Wires':
"Whenever I heard any hiss of communication, I’d hold down my Transmit button. That would send
out a radio signal on the same exact frequency, which would jam the signal.
Then the second agent wouldn’t be able to hear the first agent’s transmission. After two or three tries back and forth, the agents would get
frustrated with the radio. I could imagine one of them saying something like, “Something’s wrong with the radio. Let’s go in the clear.”
They’d throw a switch on their radios to take them out of encryption mode, and I’d be able to hear both sides of the conversation! Even today
I’m amused to remember how easy it was to work around that encryption without even cracking the code."
Mitnick's hack probably wouldn't work today but I don't know the specifics of who he was listening into nor with which gear he was using. Most P25 networks these days are set up with trunking, so the conversations hop around a bunch of frequencies at random. Holding down the transmit button would do nothing to interfere with the conversation taking place. Even with sophisticated gear you wouldn't be able to who was transmitting at any given time so you'd have to be willing to jam all the frequencies in a group.
Of course, P25 systems are still sometimes set up without trunking so in some situations it might work.
My mom had a rural dialup connection that typically managed about 30kbps. 15+ years ago this was enough to load Facebook, Gmail (even without its fallback basic html mode which is gone now anyway) and so on. You just had to be patient the first time while all the graphic assets got cached.
Some years later she was on a cell network connection with 128kbps fallback if you go over your limit. Hey, 4x as fast as she had before, effectively unlimited right? Wrong. Bloat was by now such that sites simply wouldn't load at 128kbps. Things timed out before all the bloat was loaded and you would not get the UI regardless how patient you were.
Hacker News still worked of course.
The fallback HTML mode for web search is still there (two flavors even!). You just have to pretend to be an ancient browser.
Using a user agent for something like Firefox 6 will give you a stripped down but still basically modern look and pretending to be something really ancient will get you another, even more basic, HTML version.
I left long ago but the web search team at Google was always pretty serious about making sure you could access results, even from your ancient Timex Sinclair that you hand-whittled out of mammoth bone or whatever.
Gmail is a different story. The old HTML mode is still there but is hard to get to and is supposedly going to be phased out. IMAP still works though.