Was just looking at the app and I've noticed it says: "Give friends $64 Towards their first stay"
Which means that they have doubled the referral credit, basically now its enough for 1 FREE night at lots of places.
Doesn't appear to be appearing yet on the Android app, you can login via the website however to view the new offer.
iOS app terms appear to indicate a $75 USD (or equivelnt currency) Minimum spend.
Website Terms appear to indicate a new minimum spend of $256 to use the $64 credit As per terms here
Min spend is $200USD !