@James402 who knows.. maybe he opened the account but never used it because he was traveling with someone and they booked with that person account, or it may be some other scenario. It is more or less the same as he joined Airbnb yesterday or has one or two reviews
You can always ask your potential guest few questions before they arrive and you can ask him to show you his ID (and you can photocopy ) ones he arrives.
It's up to you and what you feel comforatble with - about 50% of our guests are new to AirBnB and have no reviews. Many have been a member for a few years before finally taking the plunge. Remember guests can be just as nervous about hosts as we are about guests!