I think the thing that concerns me about the expansion of Google's empire and the interlinking of multiple services is privacy. Whereas previously only YouTube knew what I YouTubed and only Google knew what I Googled and only Facebook knew what I Facebooked, the steadily all-encompassing web of linked services means that one company knows everything I search, post, and say. There's a reason the idea of governments invading our privacy disturbs us; it should freak us out just as much that a private corporation is slowly attempting the same thing - to collect/have access to information about every facet of our lives. Even assuming it wouldn't be abused by Google (fat chance), if they own everything and all those services/information is linked together, the potential for catastrophe if their servers go down or, god forbid, they're hacked is limitless.
Furthermore, I don't think monopolies are ever good, on multiple levels.

So while I agree it doesn't necessarily mean Twitch itself will change all that much, I do agree that the general trend is worrying.