There has been some talk that Sony's plan to add movies to the PS3 is in trouble without the other movie companies on board. For instance, this was mentioned on the The Game Reviews blog where they state "it is obvious that Sony will need their support in order to give the service any real weight." I have to laugh at this type of concern. The reason is simple, look at all the other online movie services (ex. MovieLink, CinemaNow). If Sony can guarantee that their whole archive of movies will be available in HD (720p at least) over the internet, they won't need anybody else's archive of movies. Then the other movie companies will be desperate to get their content onto the system just like with iTunes.
However if this is going to be another half-baked service, then yes they need other companies to offer their own half-baked archive of movies too.