Google+ cannot be undone.
hubski.com
hubski.com
Google is competing with Facebook for mindshare and social graph information here, but Google+ could fail spectacularly, and people would just say "lol, Google can't do social" and keep using their other dozen market leader products. If it succeeds brilliantly, on the other hand, then people will have no _reason_ to use Facebook et al, because they're getting that need filled in the course of their other daily tasks which happen to include Google. To assume that Google+ is Google's most important product ever and that all future products will be beholden to it is to view Google as a social network company, which is entirely wrong. If Facebook was trying to launch an integrated search engine or a GMail competitor, then I would absolutely agree with you - those products would be inherently limited by the requirement that they tie into and feed back towards Facebook's core platform, but that isn't the case here.
I see where you are coming from. However, given the potential overhead of running a social network, plus the revenue that might come with it, do you think that Google's priorities might evolve, -that they might morph into a social network, taking their other products with it?
As far as overhead, I'd suspect that Google+ isn't even a blip on Google's overall radar in terms of overhead - the latest Netcraft survey puts Google as running 4.6% of all webservers on the internet; while it's certainly a large undertaking, Google is at such massive scale already that I don't think deploying a social network necessitates a severe shift in focus.
I think the privacy issue is the Achilles heel of Google+. Remember when anonymized queries were released for research purposes were released with gems like "kill my wife zipcode 94234". Well, now you have everything in one package: your location, searches, email, business infrastructure (if you use Google apps), pics, etc.
Google+ is the end of the "don't be evil" era. Not because they are evil now but because they're pulling out all the stops and not putting data in silos (even for show). Google+ is a lot more scary than Facebook because of the algorithmic component.
Going forward, their products will integrate with Google+ by default making it harder and harder to divest yourself from being tracked. They will make money off of this information, the question is how.
Like wise you can write a whole article about how Google standing by and doing nothing while Facebook dominates the social network scene is a mistake.