Welcome to WebmasterWorld Guest from 126.96.36.199
My guess is that they either have their own bot doing it or are paying someone to do it for them. Apparently (although I've not noticed it), this is a new form of viral marketing some companies are resorting to.
For example, a referrer of:
is almost certainly logfile spamming. Not easy to detect if you just own the one domain; but when you own nearly 50 and see the exact same referrer to all your domains within a relatively short period it stands out a mile.
Just add them to your mental list of companies to never do business with.
adds: the DMOZ data dump seems to be a common source of domains to go logfile spamming on...