My DS will be 3 in August.
He's been out of nappies at nursery for a few weeks now - only wears them when he has his afternoon sleep. My parents look after him 2 days a week too, and he doesn't wear nappies with them either.
But with me he still wets himself! He's fine if he's got a bare bum - he'll happily use the potty. But if he has pants or trousers on, he wets them. I haven't made a big deal about potty training at all, and I never tell him off. I ask him intermittently if he needs a wee, he always says no, and then sometimes he'll wee in his pants 2 minutes later.
I don't think it's an attention thing, because he'll do it even while I'm playing with him, or if he's having some quiet TV time.
Any ideas why this is? I'm starting to think I must be doing something wrong!