Cats and their liking for cannabis
Cats, for some reason, seem to find that the smell of cannabis does something to them that's not dissimilar to what catnip does, but it doesn't happen with all cats (then again, not all cats are fans of catnip).
One of my cats took it a step further though; in the past, I've received totally fresh flowerbuds from a friend (fresh as in not even dried, freshly cut from the plant), and one Saturday morning, after I got out of the shower, I saw him almost climbing inside the carrier bag containing the fresh buds. When he emerged, he had a half chewed bud hanging from his mouth; he consequently spent the rest of the weekend behaving as if he were in a Cheech & Chong movie (falling asleep with his head in the food bowl was the highlight - if you can call it that).
Considering cats have a different metabolism to us (eg paracetamol is incredibly toxic to cats), I wanted to make sure it wasn't doing him any damage. I eventually found an Aussie book about cats, that was written by a vet: It didn't have the all drugs are bad approach, and mentioned that some cats do have a liking for the smell, some even enjoy getting stoned, but that overall, cannabis is no more toxic to cats than it is for humans. With that knowledge, I now let him examine "the goods" whenever I get some freshly cut plant material (he doesn't get anywhere near as excited by dried plant material). Sometimes he just rubs his face in it, but other times he'll chew a bit as well (I can tell by how much cat drool there is on the plant material!). None of my other cats are that interested in it, but some of them really like the smell of valerian root (sweaty socks!!). Just like people I suppose.
BTW, cannabis isn't so benign for dogs. One of the components present in cannabis (cannabichromene) really badly effects a dogs sense of balance, to the point where it can make them quite ill (imagine a person with reallly bad motion sickness/seasickness); they can fall over and hurt themselves.
While I in no way condone people who give drugs to animals (for those people: unless you know about their different metabolic routes for drugs, you could easily kill them with something you thought was 'safe'; so don't), if an animal is determined to indulge (and it's not toxic to them) I can't see why you shouldn't allow them the oppertunity every now and again, as long as they don't eat the lot!
PS. That doesn't go for chemicals, as opposed to plant drugs. People know that they can ruin lives, but still indulge to excess; animals don't, so keep them well out of the way, and never let animals have any access to them.