(Psst! Java... A programming language that runs on most machines, very small file sizes, and very fast)
The file sizes aren't small when you consider users who don't have Java installed (Windows does not have it installed out of the box).
A user downloads your nifty 1 MB program and then discovers it needs a 50 MB Java download to operate.
I would also dispute fast, unless you have a JIT compiler on your platform. Otherwise, the bytecode is interpreted. Faster than SilverCreator, sure, but you could still do better in C/C++.
Java runs on basically
all machines, but that is also a bad thing, because you don't get consistent user interfaces on each platform. If you write your Java app on Windows, it's going to look pretty lame on the Mac.