Well I think there was no need to have separate accounts to begin with. YouTube and Gmail had different accounts because YouTube was a separate company.
I think having the option for separate accounts would have been best.
I try not to post anything on Youtube or favourite videos or anything because it's tied to my "real" Google identity which is very traceable to me.
For the same reason I try not to link my Facebook or Google accounts to games and stuff I can help it (though I've mostly given up).
I did have a "fake" Facebook account for lots of stuff that wanted access to my Facebook feed and it's craptacular. Same for Google, but switching accounts for Youtube is a hassle,
I work for Google but opinions are my own.