No need for a Chrome extension. Just block the /ajax/mercury/mark_seen.php, change_read_status.php and /ajax/messaging/typ.php URL's via your firewall ruleset.

No need for a Chrome extension. Just block the /ajax/mercury/mark_seen.php, change_read_status.php and /ajax/messaging/typ.php URL's via your firewall ruleset. The utility of a kernel space firewall is not limited to Facebook privacy. It's very easy to stop mobile apps from "phoning home" using such a firewall. Could users find this desirable? Maybe there's a market for a pre-configured firewall you can carry in your pocket? Think small PCB (say, RaspberryPi or something that could fit in an Altoids tin) as a headless wifi gateway/firewall for your branded, infinitely functional, graphical mobile device. It might sit between the user's mobile device and the wifi access point and redirect certain IP addresses (e.g., those for www.facebook.com) to a proxy listening on localhost. The proxy can perform Layer 7 filtering. tcpdump/ngrep running on the PCB could show the user what apps are phoning home. The user could then choose to add them to the firewall. Internet service subscribers with modest technical know-how routinely configure and run wifi routers in their homes. Or someone does the config and setup for them. Running a similar "router" in your pocket is not unfathomable. Does privacy have value?