Windows only. getData/clearData/setData are only implemented for drag. There is a fixme in ClipboardWin.cpp: //FIXME: Need to be able to write to the system clipboard <rdar://problem/5015941> I didn't see a bugs.webkit.org bug filed on this, although this is clearly a known bug since there is a rdar bug.
Updated: getData does work for copy since it is just a read. The functions that do writes (clearData, setData) are unimplemented for !dragging.
*** This bug has been marked as a duplicate of bug 17645 ***