Most users don't care. They're not thinking about the wider implications of Google having all the information Google+ will accumulate. That's completely incidental to their goal, which is to keep up to date and share stuff with their friends. And they want that to "just work".
They want convenience, which means not wanting to have to get past obstacles like logging into a completely different site to share a file. Even if the UI Google offers is a bit more sucky than the competition, e.g. dropbox, not having to go to the competition in the first place can easily be enough to make the Google experience the overall winner.
If they think about the "eggs in Google's basket" problem at all, many will see that they give Google all their personal info (name, dob, email address, location?, etc...) to use Google features, and they give Facebook all the same personal info to use Facebook features, and they give some other company a subset of their personal info to use, e.g. file-sharing features, etc.... Seeing as how Google already has the personal information they think about when they think about personal information, it won't occur to them that the meta-information Google will get from tying together. Rather, 3 or 4 companies have their personal information now, and they could reduce that to 1 by doing everything with Google.
My longterm strategy is to use different companies for different services. It is a slightly bigger hassle than to have everything integrated by one company, but not that a big hassle, after all. My goal for the future is that Google will own only my search strings, and not much else. I would even like to replace Gmail, but didn't find an alternative yet (but live.com looks promising).