Because of this, my Gmail contacts could see the comments I'd made on Youtube videos because it was front and center of their G+ profile page, which I recall popping up when you logged into Gmail. Prior to this, there would have been no organic way for them to discover my comments other than randomly coming across a video I'd watched and commented on.
Now, I don't post anything objectionable on YT comments (it is attached to my primary Gmail after all), but I wanted to keep my YT experience separate from people on my Gmail list. G+ took that away in one fell swoop.