@timcliff said this in the comments: "To clarify too though - there is the Steem blockchain, and there are the Steemit servers. The Steem blockchain is the decentralized network where all of the posts/votes/etc. are stored. The Steemit.com servers are hosted by Steemit, Inc. Steemit, Inc does store a local copy of the images - so if your third party hosting site goes down, the images for the posts should still load, but Steemit, Inc can be censored - so images stored there are not as "safe" as what is on the blockchain."
Also, did you see the comments by craig-grant? While I still would like to see a more fluid system with safeties in place, I know there are so many issues the administrators have to work out. Craig gave us a link to a much more secure form of uploading, the creator of this image hosting site is on steemit, here's his original post: https://steemit.com/dirtyimg/@blueorgy/dirtyimg-steemit-temporary-image-hosting-solution-utilizing-steemit-image-caching