The Shared Suffering Hypothesis

This applies to programming too. Even though Java/JEE has such a huge number of programmers, every Java project I ever worked on was probably unique in the combination of libraries it used (ever worked on a project with struts, spring, ibatis, oracle portal and prototype? Good chance you're a ex co-worker.)

When I switched to Rails, the problem of finding people with the same problems as I had, simply disappeared. And that's the biggest argument against alternative runtimes and frameworks - even if they're a lot better, you'll lose the shared suffering, and that matters.