I've learned a lesson recently & am interested in whether my experience is shared by other hosts.
It seems that someone with no reviews (but who isn't a new Airbnb signup) is almost guaranteed to be a bad guest.
Since its so risky for hosts to leave a review for bad guests (who will correctly assume you haven't said something positive & will probably leave a 'retaliatory' review), it now seems that giving someone no review is the equivalent to giving them a bad review.
I accepted someone in the past who had no reviews & they ended up being terrible guests. But I thought I'd take the risk again recently on someone else who'd been on Airbnb 4 years with no reviews. I am still getting over what they did to my home.
My luxury property was left an appalling, disgusting mess. Every single thing not nailed down was moved into different rooms (including all the furniture & contents of all cupboards/closets/cabinets). Leftover food, crumbs, wrappers etc throughout the house on the floors. Wet patches on rugs where they'd spilled drinks & not even attempted a clean up. Every single item from the kitchen was dirty & left throughout the house. Snotty tissues all over the floor in every room. They slept on top of the beds (not between the sheets), and left stained linen & towels. And this was all accomplished in a 2-night stay by a 'normal' family (parents in their 30s with kids, not some raging party of teenagers).
In the future, I will absolutely reject any booking from people with no reviews (unless they're a brand-new Airbnb user, in which case I'll ask a LOT of questions before deciding if they're worth the risk.) Better to forego the income that have this happen again.