I have NOT received this email, but other hosts claim to have received it, and others have had similar discussions in phone conversations with AirBnB support. This is related to (and explains) the recent issues that many hosts have reported in which their listing would only appear for searches of 3 or more days, but not for searches for 1 or 2 days. (Apparently, AirBnB was testing the upcoming change without informing the hosts.) Anyway, here is the text of the email. Note, again, that I have NOT received this email and I can't verify that it's legit. I suspect it is, though.
"At this time, we're experimenting with getting more high-value bookings by filling your listings' calendars more strategically which is why your "XXXXXX 1 BR - great neighborhood!" listing will only show in August for searches of 3 or more nights. This is a permanent change. This change will make the listing's calendar open for longer-stay searches. In the short term, your calendar will be more open than before, but as time goes on, the unbooked days will be filled up and the overall impact will be at least neutral."
If this is an actual upcoming change, W.T.F.???
