Brings up an interesting question (for me, anyway)- how worn can a fretless fingerboard get?  So much that there are noticeable grooves under the strings?  I imagine it wouldn't be too difficult to sand it down a bit and refinish.  I have a fretless, but I've used only flatwounds.  I've never noticed any wear.  Maybe I need to play more...
 
http://newyork.craigslist.org/mnh/msg/964691560.html

That's probably the one that's also on TalkBass.  It was listed there as defretted as well, so a good price if you can accept that it is a well-played bass that isn't factory fretless.