Offer a return payment for them of a few cents each. It's how a lot of highways & cities in the US stay clean of aluminum cans - the homeless pick them up and turn them in for a profit.

Exactly. In Germany, return payment is 0.25 EURO and it works great. Most people at home collect them and bring to supermarket. Those who throw them on streets, homeless people are more than happy to pick up and cash in. Win-win situation in every angle.

They are nice thick ones as well. I usually bring one or two home from Germany, as they are far better suited for reuse when hiking than the crappy ones you get here.

What about going after the tossing instead?

Why not do both?

Because I think you shouldn't take deciding what other people are allowed to do lightly. Such things should only be done in extreme cases, like self defense or, perhaps, to prohibit ruining nature through littering.