Earlier quoted context omitted.
I assume they couldn't be honest because it would've violated Craiglist's Terms of Use, namely: You agree not to post, email, or otherwise make available Content: k) that constitutes or contains "affiliate marketing," "link referral code," "junk mail," "spam," "chain letters," "pyramid schemes," or unsolicited commercial advertisement; l) that constitutes or contains any form of advertising or solicitation if: posted…
I assume AirBnB have received many cease and desist letters from craigslist. Craigslist is just waiting for AirBnB to get bigger so they can get big chunk of money.
They sent a cease and desist relatively early on (not waiting until we got bigger).
It's likely that they didn't know and have either just sent them a cease and desist or AirBnb has chosen to ignore it.