Google+ Failed because it did not provide any added value to the users.
Too much integration of services is actually lowering the value, I don't see any value between which YouTube videos I have commented on and which searches I have performed.
There is also a danger with too much integration - privacy matters, and if things are too integrated then it's a goldmine for anyone with malicious intent. If services are separated then each service needs to be targeted individually, which raises the stakes.
Of course - Providers of integrated services are obviously able to do statistical analysis of information that's valuable for marketing purposes, so that the ads that you will see when reading your favorite sites without an adblocker will be targeted for your specific demographics. There's usually no point in offering Viagra to teenagers or trendy boots to people in their 60's.
Maybe it's also a question of the personality of people, which means that you end up with different personalities:
- Facebook, a heaven for narcissists, people with a selfie stick and similar.
- Google, people that actually do things and in some cases show what they have done through YouTube.
- LinkedIn, an address book and CV online for professionals.
- Bing, a place for people unaware of technology and other offerings.
- DuckDuckGo, a place for semi-paranoid people.
- Tor, users that are either paranoid or performing illegal/semi-legal stuff.
Due to the bell curve we of course see people mainly using Google as Bing and DuckDuckGo users from time to time. But people frequently using DuckDuckGo are less likely to be on Facebook.
Also just ask yourself - do you use more than one browser? That's one way of breaking the statistics collectors to ensure that you show a different profile depending on what you do on the net. It's not a perfect safety, but it will shake up the statistics a bit and reduce the risk of cross-site reading of cookies trying to track your behavior. Personally I run Firefox, Opera and IE depending on what I do.