Right now, our implementation of CSS custom cursor hotspots is only enabled in strict mode. The original implementor (Rob Buis) and reviewer (Eric Seidel) do not remember why it was done this way. Neither does Hyatt. I can't find any information in the spec indicating that hotspots should be strict mode only, and furthermore, Firefox implements hotspots in both quirks and strict modes. I have a patch to post shortly!
Created attachment 32978 [details] Patch In Radar as <rdar://problem/6554340>
http://trac.webkit.org/changeset/46061