16-bit address and data buses? Hardware multiplier, divider, and barrel shifter? I wouldn't exactly call it simple. The cost to build one out of discrete logic probably approaches the quadruple digits.
Magic-1 (http://www.homebrewcpu.com/) is a 16-bit, microcoded homebrew CPU that took about 4 years to build, and it doesn't have any of the above features.
Who will implement a DCPU16 in Conway's game of life?
Seriously though, the fact that we're able to ask questions like this is a breath of fresh air... as a market, Notch has done a hell of a job appealing to us.
What's the hype about this DCPU16 thing? The game hasn't been released yet and people starting to write assemblers. Are you totally bored out of your life?
There are dozens of reasons people do things like this. It's good programming practice for those of us who aren't as confident in our abilities. It gets you some notoriety in the community, maybe even a community you're a big part of. It's something that can go on a resume really easily, if used.
Or maybe, you just wanted to have fun so you spent a night doing this. It isn't a big deal. If you don't waste one night of your life every once in awhile, you're pretty unlike the rest of humanity.
The DCPU was designed to be easy to emulate. It's a lot of fun to hack on, and simple enough that you can write assemblers for it and still have a life. :)
https://github.com/judofyr/rcpu
It's a DCPU assembler (written in a Ruby DSL) and an emulator/debugger (which allows you to step/run through the execution).
Next up I'm going to implement library support and write some I/O functions. Much of the code is already in place though (e.g. https://github.com/judofyr/rcpu/blob/master/examples/screen.... which maps 0x8000-0x8400 to the terminal).