A coffee machine shouldn't have to also produce cups, or whatever.

Beyond that, I would say the designer of a coffee machine should make as few assumptions about cups as possible.

And I've got a case in point too. Recently, we got rid of one of those machines that outputs a little cup filled with coffee and replaced it with one where you insert your mug, stick a little packet in this slot, choose one of three "bodies" (espresso, regular, or choco) and the machine outputs the coffee directly to your cup. That would seem like an improvement right? Except that just the other day I found that my travel mug doesn't fit in the machine. Now, I can't even get the output in a little cup and pour it into my travel mug.

Wasteful or not, with the old machine I got my coffee. Now, it's true that in the real world, where you find coffee machines and the addicts who frequent them, it is arguably more important to do away with waste than it is for every caffeine junkie to get his coffee. But, in the world of software, a working coffee machine object that was a little wasteful would likely trump a super-efficient one with a bug such that, under certain conditions, it would not allow you to fill your cup object.

-sauoq
"My two cents aren't worth a dime.";