There's a great article about why you should develop for the web on Tim Bray's site. He says developers who write software for specific platforms or OSs are like sharecroppers; they pay to farm on other people's lands, and are at the mercy of the land owners. I agree with a lot of what he's saying. I once wrote one of the first free MP3 players for the Mac, which was pretty popular (got 10k downloads in a few months even though it was only released in Japan and was buggy as hell) because it was one of the best (as crappy as it was) free MP3 players avaiable back then. But then came Apple with iTunes, and that was the end of that. Actually, the other half of the story was that I got bored, and started working on IlohaMail.

What I really like about PHP is that it's a cross platform technology through and through. People are installing IlohaMail on all flavors of Unix-based OS's, from Linux to Solaris to OS X, as well as Windows, and it's accessible from any platform capable of running a modern browser. It's nice to know that my work goes out to so many people, instead of being limited to 2-4% of the global audience. And the really cool thing is, I'm still seeing an upward trend in demand.