"Another reason why Google+ competes with distributed social networks: for people worried about the social networking service provider (or the Government) reading their posts, client-side encryption on top of Google+ could work. The Circles feature is exactly what is needed to make encrypted posts viable, because you can make a circle of those who are using a compatible encryption/decryption plugin. At least a half-dozen such plugins have been created over the years (examples: 1, 2), but it doesn’t make much sense to use these over Facebook or Twitter. Once the Google+ developer API rolls out, I’m sure we’ll see yet another avatar of the encrypted status message idea, and perhaps the the n-th time will be the charm."
I really like this idea. I hope they even implement it themselves so you can encrypt the data yourself on certain circles.
I also agree that Google+ so far seems that it could threaten not just Facebook, but also Twitter and Linkedin and maybe even personal blogging (Tumblr, Posterous, Blogger, and Wordpress to a lesser degree)
It could become a publisher platform too if they create a good way to monetize the content without being spammy. Chris Brogan suggested affiliate links. I was also thinking they could allow you yo use your own Adsense id on the page of the post.
But they should think all these things through before they implement them. Oh, and I'm STILL waiting for content search within Google+, the way Twitter search works.