ummmm is right about Twitter being funny. I remember some great gags about Tesco's horsemeat (one of them as I recall was "I've just looked at the burgers in my fridge and ... they're off!") and the photo someone posted there of a tube station control room being accidentally flooded with quick-set concrete (one of them suggested it must be the Blue Circle Line).
At its best it's like watching a really good improv show. You don't get that sort of instant repartee on AB.
That said, most of Twitter isn't like that, there are plenty of cute kittens.