I get the right tool for the right job mantra. I've used it time and again in my analyses, but typically with regard to which components to use in a large-scale complex distributed system. I've tried to apply this mindset to programming, but just don't see it. Why can't I use the same programming language inside my browser (no plug-in), to develop a browser plug-in, on my desktop and on the server? I'm not fussy as to which one it is, but it needs the appropriate support libraries for each platform. However, our choices today are limited:

Possibilities include:

1 - Adobe Flex. With AIR I can build a browser plug-in and a desktop application. However, I cannot write Flex directly in the <script> section of my HTML and I don't think it would perform well on the server.
2 - Javascript - I can use Javascript inside the browser and performance is being continually improved. And, while some have embedded Javascript into their applications, e.g. jBPM, the library support for desktop and server applications just don't exist.
3 - .NET - .NET gives me everything I need, but I'm pretty much trapped on the Windows platform. Yes, there are ports of the .NET environment on other platforms, but they are certainly not plug-n-play. Moreover, .NET doesn't play particularly well outside of IE.
4 - JavaFX - JavaFX isn't Java. It's designed for rich internet application development and uses a different language. So, even Sun cannot provide a single programming solution.

Other server-side scripting languages, such as Perl, Python and Ruby could all be good solutions, but none of these work natively in the browser or even run as a plug-in.

I'm curious, am I the only person who would prefer one programming language to build an entire distributed application that leverages the Web and runs across all platforms?