Facebook is the biggest privacy violator out in the open. Short of hacking into people's lives, Facebook has been notorious in getting users to share information that they thought would be only available to their "friends" and upselling it to advertisers. With Google Plus, I hope Facebook finally get the nice hard kick in its "you know what". However, for Plus to be a viable alternative to Facebook, it would have to be very discrete with user information and truly "do no evil" with regards to privacy.
Right now, it's off to a bad start. See with Circles in Plus, users are able to control what information they share with their friends. However, this morning, Gizmodo reports that the "resharing" feature is on by default allowing your friends to share your information. I can see in some instances why Google would want to do this but not everything we put out there is for "resharing".
I've come to the realization that what we put out there on the Internet, to one degree or another, is quite public. Some more than others. However, what Facebook does is blatant "f-you" to its users and Google needs to pull back from that. After all, it's copying virtually all of Facebook's features as well as its looks. Given users assurance regarding their privacy is the only differentiator it has.
Otherwise, why would anyone switch from Facebook?
As for mobile users, Android users have first tries at the native app for Google Plus. I reckon the integration will be much tighter than Plus will be on other services. As of now, Plus is sitting in Apple's app store approval purgatory. It'll probably be approved. And I know lots of us will be "checking in". The "resharing" issue and other potential privacy land mines we don't know about yet could really make a diff between Plus being a Facebook killer or just another "Wave" or "Buzz" screw-up.