No need for a Chrome extension.<p>Just block the /ajax/mercury/mark_seen.php, change_read_status.php and /ajax/messaging/typ.php URL's via your firewall ruleset.<p>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?<p>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.<p>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.<p>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.<p>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.<p>Does privacy have value?