Did it land too hard?
Was the probe damaged when it landed on the planetoid? Did it come down too hard?
If it didn't get any surface samples and they can't try again, then I think Hayabusa should stay around Itokawa and study it as much as possible. They should even try to land it one more time for surface studies and images.
Whatever happened with Nozomi, which never made it to Mars orbit? Are they still in touch with it? Can the probe still do some interplanetary region exploration?