I was shopping with my sister and her 4yo DS yesterday and he had a tantrum to end all tantrums in Target when he wasn't allowed to have the $100 Thomas station he wanted. The screaming was unbelievable, absolute hysteria that he couldn't snap out of. My sister tried to tell him reasonably why he couldn't have it (and maybe to ask Santa etc), then tried "you're shouting and I'm not going to listen until you're speaking quietly", then tried to walk off and leave him (while he swung on her shirt and skidded on his heels) etc. He's getting too big to just pick up and walk out of the shop. In the old days he'd have got a smack and dragged out by his ear, but you can't get away with that now!
DH and I were talking about it last night and trying to work out what we'd do if our DS does that at that age. It was 2yo tantrum behaviour but 2yos are much easier to physically manage!
So what would you do?