People put too much trust in even their home internet connections. A few weeks ago my home internet connection (Wave-G delivered via ethernet(dhcp) to my apartment) stopped working. I noticed instead of my router having its normal public ip, a 10/8 address had been assigned. After poking at the router address from the dhcp reply, I found myself looking at a Comcast cable modem.

Turned out a neighbor had moved in, and for whatever reason plugged the LAN side of a cable modem into the ethernet port on their wall, and had begun fighting the ISP's dhcp service.

Wait... your neighbor had an ethernet port in their apartment that was shared in your apartment? That's not a home network, that's more like a MAN (or Metro Ethernet or something). That ethernet port in your apartment should 100% be treated as hostile if that's the case.

The building has a shared ethernet fabric with a wireless uplink. With this configuration (and it isn't an uncommon configuration), anyone on the ethernet fabric can throw up a dhcp server and assign addresses/rutes to anyone else (or a number of other attacks).

DOCSIS has had similar issues in the past -- folks on the same node could directly pass frames between each other, and in some situations you could sniff your neighbors traffic.

My point was that whether you're at home or out and about, you shouldn't trust the "quality" of your internet connection, and should focus on having end to end encryption with whatever service you're attempting to communicate with.