I used to have that concern as well, but then I realised I didn't actually get that much value from yt recommendations. The stuff I want to see comes from channels I'm subscribed to and only very rarely have I discovered something good from recommendations - most of the discovery comes from the right-hand side video column.
The last rec engine I got much value out of was early Netflix, around the first public competition to improve their engine.
My nightmare is that corporations suddenly realized that recommendation engines don't actually help them sell content. Maybe it's easier to persuade tons of people to watch something they'll all think is "good enough" rather than to identify or develop content some tiny subgroup of people will think is sublime.
Did anyone ask for; "What did you think of this video?" 5-star feature, or "Recent Posts" ie. "Hi guys, i know i haven't done a video recently blah blah".
It appears they are repeating the same mistakes made on G+.
I'd assume that data is being used for training somewhere.
For example, I kept seeing Starcraft 2 replays on the homepage after watching the AI vs human tournament which kept helping me procrastinate. I don't even play the game nor subscribe to a single SC2 channel.
Cleared history, started off strong watching some of my language-learning channels, and now my Youtube homepage is pretty productive.
This doesn't make much sense to you until you realize one of the biggest groups of video watchers on YouTube is toddlers.
Bullshit.
If I start a random video and let it automatically progress to the next one, I will have to watch it (or parts of it) to tell if I’m interested or not.
This is particularly annoying for Youtube music where starting a radio from something you like now is guaranteed to add new artists to “your artists” because you listened to them once, only to click “next” or “not interested”.
An example of this is Blue's Clues, initially producers/scheduling were afraid that by having reruns in the same timeslot would doom the show. Instead kids being able to watch the shows again was a great boon to their target audience's enjoyment.
Ignoring that kind of direct and obvious feedback is crazy.