Thank you for all the comments, everybody! It's a seemingly small thing, but will make an unbelievable impact on the environment.

As for droughts and repercussions on restaurants, I'm not sure what to think of reverting to disposable. I guess it's out of necessity. As a consumer, I would take a stand by not eating out at all. Yes - the ultimate loser in this scenario is the restaurant and its employees (because eventually it would have to shut down if business slowed), but....does anybody have any ideas of how to get around this?

And Dwight, I agree: let's attack the big problems (like gasoline consumption) to make the big headway. But my question to you is (and this is in no way an attack): you burn two gallons of gasoline a day. How will you stop doing that? (It is possible, but will you or can you)?  And if you can't, then although a little harmless coffee cup may seem a pittance in comparison, is it reason enough to throw your (not yours - anybody's) hands up in the air and consume wantonly because you don't think it will make a big enough difference?

(again - this isn't personal, as you said you avoid disposable cups out of principal. But I think there are some people out there who may feel that the small things are too insignificant to address).  

Remember the butterfly effect.....even a little butterfly flapping its wings can change climate patterns around the world. So can we with coffee cups.