Surely, if you're going to use someone else's bin, because it's convenient, you at least have the courtesy to pick the correct kind of bin for your rubbish?

No, because people either have enough courtesy to not use your bins, or they have no courtesy at all.

Today I was wondering why people will take their shopping carts and stick them right next to the cart return, but refuse to put them in. I understand being lazy/rude enough to just leave the cart wherever your car was parked. I do not understand putting in enough effort that you could have put the cart away, but NOT actually put it away.