My reason for not writing a negative review is because before staying at their place we exchanged phone numbers and other things, and now I don't feel comfortable writing a negative review and possibly having a confrontation. YMMV but I avoid writing negative reviews despite the 'double blind' review system.
Always contact them through AirBnB. You should be treating it just like contacting random strangers for sex on Craigslist, potentially dangerous. There's no reason to give a random stranger your personal contact details.
