My own experience with youtube was the same as the OP. This was several years ago, and youtube has changed a lot since, but it looks like the more things change, the more they remain the same. I had a semi-popular channel, nothing spectacular, about 100,000 channel views and maybe a thousand subscribers. At the time it was not bad for a guy who just posted some of his own sports clips.
The entire channel was yanked one sunny day, without any explanation as to why and no recourse or way to appeal. The automated support was entirely useless. I could not get a hold of a human, or at least, an e-mail address. There were none to be found. Youtube, as it appeared at the time, was entirely ran on automatic. It is, on one hand, understandable for a site that receives several years worth of uploaded material each minute. On the other hand, it was a thoroughly frustrating experience as I have done absolutely nothing wrong. To this day I have no clue as to what happened, my best guess is that someone reported me for the evulz, and that was enough.
I tried again to rebuild my channel with new material. About 6 months later the same thing repeated, at which point I gave up and never registered again.
The moral of the story is: you have to be corporate big, or you have to self-host. Otherwise, you are always at risk.