It does say right on the front page: "Showcase and discover Microsoft Word, Excel, PowerPoint, OneNote, Sway, Minecraft world and PDF documents for free," so it's pretty clearly intended for public distribution of e.g. document templates. On the other hand, how on earth did MS release it and let it live without noticing that people were using it completely wrong? They should have quickly noticed that people were using it to exchange sensitive documents, then pulled the service and redesigned it so that sort of behavior became exceedingly rare.

Even sophisticated users will misuse these services: remember the fad of putting all your dot-files on Github, when a bunch of people uploaded their Amazon credentials? This is giving the same opportunity to much less sophisticated users, with predictable results.