for each photographic session, even if you shoot a model or models on a regular basis you will need a new release form for every new shoot.
and you need to make sure the model gets a copy of each release, not to mention images (either in print or on cd) when it is tf/p/cd. obviously when it is a paid shoot you need to pay the model.
seems to me that there are some photographers out there who have forgotten this and deem themselves 'godlike', putting up images without a new model release and then crying foul when the model is not impressed with this action.
and people, remember most photographers on this site (myself included) are amateurs! and the models you work with more often than not have been amateur at one point or another and therefore you should keep your humanity intact when a model asks you take an image down, especially when it is of the naked nature! i know quite a few photographers who have no problems what so ever taking down an image/images when the model requests it, often for personal and employment reasons. i myself have been asked to and had no problems what so ever. this is mainly due to the fact that i haven't forgotten i am a person just like them

for the ones who make it difficult and often lead the model to a lot of emotional stress i say shame on you
put yourself in their shoes, i mean having a naked image of you on the internet with the risk it could affect your job...would you be so pig headed and refuse?
as i said, remember we are all pretty much amateurs here on da (artists yes) but AMATEURS! afterall if we were professionals we wouldn't have time to be shooting models we don't pay for, we would all be in the 'real' world getting paid for shoots

and at the end of the day, if you are unsure about shooting other people and model releases, shoot yourself

that way when you do change your mind you only have yourself to deal with
and to end this on a brilliant and positive note, here are some works from some of my favorite photographers/artists that i have worked with.......
