.25 cups.

If people want their customers to care more about the environment or whatever that shit is, they should charge them for paper cups. If you bring in your own cup, you're cool, but they should visibly and audibly announce that if they use a paper cup, it's going to cost them, say, an extra quarter. One, more people will bring in cups and two, the money they get for paper cups can go to some environmental mumbojumbo. I would of course boycott anyone who made me pay for a cup but someone might respond to this. Inspired by Slate.