Don't be a free user if you really care about the long term service provided by the provider : https://blog.pinboard.in/2011/12/don_t_be_a_free_user/
It has happened to all image uploaders in history, and it will keep happening forever, since image uploaders are 1) a money-losing business (people will flee as soon as you stop hotlinking) and 2) have no real value (how much time does it take you to write an image uploader? probably one of the first things you do when you're learning to code for the web)