No clue why they're crawling, let alone stealthily (no rDNS):
208.90.56.152
Mozilla/5.0 (Macintosh; Intel Mac OS X 10.6; rv:2.0.1) Gecko/20100101 Firefox/4.0.1
robots.txt? NO
IP = Cisco Systems Ironport Division
UAs from [
projecthoneypot.org...] data:
Mozilla/5.0
Mozilla/5.0 (Macintosh; Intel Mac OS X 10.6; rv:2.0.1) Gecko/20100101 Firefox/4.0.1
Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.8.0.14eol) Gecko/20070505 Iceape/1.0.9 (Debian-1.0.13~pre080323b-0etch3)
Python-urllib/2.4