I avoid them like the plague. On my FB I have a very few "interests" marked, but for example on Youtube I have not yet subscribed to a single channel.
I don't think they will benefit me.
If I like a Guns n Roses song, which I do, what does it benefit me to subscribe to Guns n Roses channels? It will only make me a single-tracked person.
I have also un-checked Googles personified results, not that it makes Google any more bearable for me, but it is something I feel like I have to do - to get a little bit more out of it, and make it a little less "narrowminded".
If I blindly went by Youtubes recommendations, I'd pretty much end up watching the same 10 videos over and over and over again.