Totally agree. I'm a product manager, but I taught myself RoR and MySQL last year mostly because I wanted to better understand how databases work with web apps. In the process I also learned how to use CSS, SVN, nginx, and search engine optimization techniques.

I don't ever expect to use these skills in a major web app (I'm nowhere near good enough to do it for real), but they've helped me immeasurably in communicating effectively with engineers. Wish I had done it years earlier.