I think the difference between an art and a craft lies in their limitations. Art is limited by the imagination, a craft is limited by the medium. You or I can draw anything we want, no matter how absurd or fantastic, and it won't necessarily fail due to the medium it's created in. Try to take the same approach with a craft, for example pottery, and be prepared to fail miserably.
Below is a shot of and link to Jen Smerdon's pottery - the black and white pieces are sawdust fired, the others use a more traditional firing/glaze. The shapes themselves are fairly standard, though formed with a lot of skill. I think that after a clay pot has been formed, pottery can then transform from a craft into an art, through etching and other techniques, as the medium's limitations fall away and the creator can design what they wish.
