Betfair will pay out on 3 places if eight or more horses are originally nominated for the race.

For example, if eight horses have been entered, and four are then scratched they will pay out on the three-placed horses. I believe if the final field has 3 runners or less then there will be no Place betting.

As moeee has stated, the dividends can be very skinny compared to other betting agencies, even though the strike rate can be quite high.