If you are building an OS kernel, database kernel, or writing high-performance computational code (after having prototyped a low-performance version, and made s

If you are building an OS kernel, database kernel, or writing high-performance computational code (after having prototyped a low-performance version, and made sure that the high-level algorithmic design is sound) then must be picky about the libraries you use anyway. If you are writing a quick script, then you don't want to be picking through your libraries source code for thread safety. But 99% of people who use threads are just looking to keep a GUI looking responsive, which only takes a couple of processes anyway. Sand-boxing different components into their own process seems to be the way players like Google (Chrome) and Apple (Lion) are going anyway. While threads have their place, I think it's the same kind of place that inlined assembly should be considered.