This is going to be a long question:
I'm working on creating a company to stream the latest and greatest movies that haven't reached Netflix yet. In order to do this, my plan is to buy, say, 10 Harry Potter DVDs, and rip one of them. We will then monitor how many people are streaming it and limit it to 10, the number of DVDs we have. It won't hurt the sales of the movie, because we're purchasing the correct number of DVDs.
This is equivalent to just sending a DVD to a user, just online. We won't lend out(a.k.a. stream) more DVDs than we have.
Update: How is Vidangel legal if they do just this?