When resizing a div or text area you get a IBeam cursor. This cursor should be the default pointer arrrow, at the very least. You could elaborate this and show a directional cursor like ns-resize or ew-resize if the resize direction is constrained. For more complete control, I sugest a psudo-element that lets you control the resizer. This would allow all sorts of style changes, even cursor replacement.
I agree, i'd like to be able to change the cursor when moving over the small resize corner of an element.
I cannot reproduce this with Safari 4.0.4 - getting the default pointer at <http://www.css3.info/preview/resize/>.