@Chris786, AirBnB does say that declining requests can negatively affect your ranking, but that it would take a number of declines to do so.
Let me find the language they used...
"Because being rejected for a booking is one of the worst experiences for our guests, we do factor this into Search Ranking. However, we understand that sometimes you legitimately need to decline a traveler, and we take that into account. We’re most interested in how you compare to other hosts, rather than just counting your rejections.
A single rejection will not significantly hurt your ranking, but over time, rejecting more guests than other hosts in your market will lower your ranking."