Not overlooked....
From the bottom of this page:
http://seds.lpl.arizona.edu/nineplanets/nineplanets/enceladus.html
Open Issues
-What is the resurfacing mechanism? where does the energy come from?
-Is there a liquid layer beneath the surface?
Maybe Cassini will shed some light on this. Remember, it looks smooth on the large scale but may be rather rough on a smaller scale. I think it's interesting and probably not coincidental that the surface age is similar to the age of the rings. Maybe it's been sandblasted smooth?