I think the problem is that people feel forced into agreeing with Google's decisions when they don't, and people don't like being forced into doing something. As an example, say you won't use Google+ because you don't like their account naming policies. That's fine, don't visit plus.google.com, don't use it, and it doesn't exist to you. But when Plus results start appearing in search, a product that you like, you are reminded of a community you can't participate in. This leads to resentment for search, because it is reminding you that you aren't getting the same service that everyone else is.

Facebook, on the other hand, is very easy to ignore. I killed my account there several years ago and haven't really thought about Facebook since, since Facebook is nothing but a social network and I'm not really a big social networking guy.

I think that's what's going on here.

(I would say, "people are worried that there will only be one provider for XXX", where XXX is mail or search or chat or whatever, but I know that's not true. People did not mind AOL or Windows or the three big banks, so I doubt they really care that Google is "the only game". Slashdot users hate monopolies, but I'm not sure the average consumer cares.)