[captainchaos]

In my opinion, this is not because they expect Google+ to be a true competitor to Facebook.

The addition of information in Google+ user profiles allows them to compete with Facebook advertising in a key arena -- targeting ads based on self-volunteered user information which is more valuable and trustworthy rather than trying to derive this information based on browsing\searching patterns.

Google+ serves to enhance Google's ad products more than it does to provide value to customers.

Having said that, Hangouts (which most people consider a part of Google+) is a succesful product.

[philwelch]

I would question the notion that self-volunteered information is more accurate. It's easy to "like" or "follow" something. It's quite another to buy it or make search queries that seem to lead to a purchasing decision. Which data is better for advertising?

[dylangs1030]

Well, in my experience people don't "like" or "follow" things they wouldn't mind seeing frequent (borderline annoying) updates for as a direct consequence. So while the act of liking and following might not lead to a direct sale, it's a reasonable argument to suggest that the people who do that are a good, receptive audience for a targeted ad campaign.

Ad targeting might not only be more effective, but it could also save money by not spending money futilely throwing a product in the face of users who are just not interested.

It's essentially not just a way to opt-in to advertising, it's a way to opt-out of all the other things you might not want. Whether this works 100% of the time is another debate entirely.

[dannyr]

If it doesn't work for you, it doesn't mean it won't work for anybody else.