Crash-Only Software

You can work towards making userspace crash only. Generally you want to make it stateless as much as possible, ie avoid writing to lots of files, only config databases that are crash proof.

A few people have been looking at stateless userspace eg see http://www.infoq.com/presentations/Runtime-Changes

Current Linux distros generally have too much poorly documented state in the filesystem, much of which may not be updated in a crash proof way...

The kernel (along with a modern FS) already is crash-only. Journals are designed to recover a FS quickly from any state after a power failure. The remainder of the kernel mostly is a bunch of in-memory structures recreated on every boot.

As for userspace, well, e.g. Firefox is a lot of the way there. SQLite itself is designed to handle failures extremely gracefully, and by virtue of regularly flushing most of its state into SQLite, Firefox itself achieves a great deal of reliability (although this might not be true of its cache storage, etc.).

Mac OS X has already provided a lot of the framework for applications, it is opt-in for app developers, but it allows for an app to be kill -9'ed on shutdown.

Definitely take a look at Sudden Termination as Apple calls it. It is one of the few features along with restoring apps as they were upon login means that a reboot is no longer a productivity killer.

Erlang is "let it crash", which is not exactly the same thing, but it's quite close, and just as interesting.

There is a quit option in the menu, so no. I think it can be configured to restore state on a clean exit. Chrome can.

If the default behavior isn't working for you, give the Session Manager add-on a try.