I have pinned video to IPFS, before, and it streamed well from an IPFS gateway. I lack an understanding of what the impact to a gateway would be, though, if many users were doing this.

One thought would be software that would automatically pin any video you viewed, or the partial content you viewed, for a period of time. Popular videos with many views per day would also be supported by many peers to pull from. Videos viewed infrequently might be pinned only by the content creator or a handful of others. The like/upvote concept could be tied into pinning, even on a scale such that an ordinary upvote would subscribe you to, say, 3 days of pinning, and a super-upvote would subscribe you to 20 days.

I can’t figure out where to enter credentials. Trying various menu options yields the message “Login first” - OK, but where?