Comcast of all people offers the ability to buy movies on demand. Not just rent but outright purchase. If you leave Comcast as a customer, you can have every purchase mailed to you as either a DVD (SD) or Blu Ray (HD) purchase
Steam has provisions in place that if its service ever gets terminated to allow users to continue to use games they've purchased on the platform. They also allow users to continue to download and play games either removed from the store or no longer sold (Alan Wake and Deadpool being two examples in my own library)
Conversely Microsoft's Xbox will de-list titles and make them excruciatingly hard to download, such as Marble Blast Ultra. Requiring you to find the game in your account history and then use that to navigate to a download page
Sony's Playstation is downright malicious with their digital store. Konami's "P.T" was offered as a free download as a teaser for an upcoming Silent Hill game
Once Konami changed their mind however, the game was not only removed from the store but actively wiped from the users console! If you connected to Playstation Network the game would be forcefully deleted from your device