I primarily use # for four things:
(1) network-connected media streaming ... I don't have to carry my music with me; this one makes sense until you realize that I travel with two Sansa Clip+ MP3 players, so I have much of my purchased music with me already.
(2) music discovery ... sometimes, I come across something I have not heard before (or in a long while); if I watch / listen several times, I typically order the CD (and rip to one of the above-mentioned players).
(3) music / video sharing ... It is better and easier to send a link to something than to try to send a whole music file (and YT worries about copyright laws so I don't have to).
(4) educational / tutorials ... I do watch learning videos, such as how to cook apple pie from scratch or how to recognize whether the scorpion that bit someone is dangerous to humans. (This actually happened. The stings from the pale yellow scorpion in the California desert hurt a lot, but do not put the victim in any danger.)

Right now, (1) is threatened by the implied message of their recent ToS/ToU change: if your channel does not generate enough visits, we may close it. I think (2) and (3) would only be affected if a whole lot of channels are shut down. (4) is probably even more threatened than (1), but since these videos often have low viewer counts, the bandwidth might be easily handled by one's own site.