In the book http://www.amazon.com/Multiplayer-Game-Programming-Architecting-Networked/dp/0134034309 , they describe a thing which is essentially a frustum-based interest management. They do acknowledge obvious problems with sharp turns, and suggest two-layer system: (a) for short distances - distance-based, and (b) for longer distances - frustum-based.

I'm wondering - are there any serious games out there doing this kind of stuff?

Bungie's Halo networking model uses this (among many other things). Check out this Halo Reach talk:

http://www.gdcvault.com/play/1014345/I-Shot-You-First-Networking

I did frustum-based for There.com, but we could never get it to work fast enough when doing sharp turns.
(Mind you, our min spec was a 56k modem ...)

I would recommend against it. I'd almost always recommend scaling down update rate when things get dense, and guarantee a particular radius be visible.
You also want to prioritize certain entities. Mainly, if you're in a group, prioritize group members; if you have targets, prioritize those of the player and her group members.