thinking of the worst case scenario to arise from such a thing (or possibly not worst, but near worst)
(1) photographer accuses model of displaying poor professionalism
(2) model counteraccuses photographer of trying to get fresh, with bad behaviour on photographer's part to dissuade her from turning up in the first place
(3) no witnesses, all agreements, etc made via phone with no records of what transpired, only individual claims
then how? how to resolve? in this case both get their reputation damaged... and no one will ever know.
for (2), don't think it doesn't happen. has happened before.... with models taking sides on whether or not said photographer has displayed good behaviour. and the fact is, a photographer who has wolfish behaviour might not try to get fresh with every model, and only pick and choose his prey.