You mean like any number of startup social networks each year that fail because they can't get the traction which Google is more likely to? It's sad, but that's the way it is - there are innovative and good social networking sites out there, but without the backing that a Google product has they keep failing.
It's a secure (SSL), anonymous (no cookies), ad-free Google interface. You can make it the default in your search bar in any browser either by hand or through an extension. Note that the results are much more minimal (no links to similar articles, cached versions, etc.), which you may prefer, as I do, or not.
Also, using a search engine directly is not the same thing as using it through one of these intermediaries (especially while logged in).
I think you hit the nail on the head. I think Google+ looks pretty neat. It's more along the lines of what I am looking for in a social network than Facebook is. But I do not plan to use it for the exact reasons you mentioned.
My searches are private. Anything I do on a social network is public. I do not want the two of them mingling. I don't want the possibility of an accident. I don't want a single entity to "own" my search and social data.
I really wish someone else had created this.