NXP announce ARMs down to 8 pins and $0.39

[poptones]

Actually, thinking about it just a bit more I can see all sorts of advantages.

You really just need a few pins. If it has SCK MOSI and MISO then it can interface to all sorts of stuff that is very specific to your needs. When you have all the pins crowded together in one place it makes board layout more difficult. If you have need for analog interfacing there's all sorts of analog stuff out there, a buck fifty and now you have 4 differential inputs optimized for your function, just have to run your serial lines to the isolated A/D. If you want to run high power lines, run the serial bus to your power driver chip and use whatever layout you need for the rest of it. For discrete controls you can run three wires to digipots for about 60 cents a control.

Actually, I think it's brilliant. Don't jam all the functionality on one part of the board, pay for the functionality you need, and minimize the glue needed to put it all together. Pretty cool.