Google as a social network has been getting a bit more play recently as they have made certain moves like giving users the ability to create vanity URLs for their profiles.
One wild card that Google has that trumps all other social networks is that it is the largest brand on the web. Furthermore, it is the largest search engine.
Today Google announced that Google profiles will start being included at the bottom of search results pages where applicable. And suddenly, a lot of people that were just using Google the search engine may realize that that they're already using Google the social network. Those with accounts may or may not see their own profiles show up in ego searches, and those without a counts may notice profiles they didn't know existed and be influenced to start one.
Those without accounts can simply google " me " and the top result is a promoted spot by Google leading to Google account profile setup.
This could potentially even help improve reputation management at least to some small degree. "When searching for yourself to see what others would find, results can be varied and aren't always what you want people to see — whether it's someone else with your name, or the finishing time from that 5K you ran back in 2002. We want to make that better and give you more of a voice," says Google's Brian Stoler.
Users who want to appear on SERPs will probably want to fill out their profiles if they have not already done so. The vanity URL is certainly an option as well, though it is unclear as to whether or not using this has any influence on showing up in the SERPs. There is room for 4 profiles on any given SERP.