Google expects more or less everybody to join. Quoting Blakeley: "They don't see it as a social network, rather a social enhancement to the whole Web. One day everyone will need a G+ account because it's practically impossible to use the Internet without using Google-owned sites." Marketers will be able simply to assume that the people they want to reach have Google+ accounts. Whether or not they are active there is another question. The +1 Button is going to be huge. "By owning a brand page and using +1 buttons on your other owned sites, you create a link between them, demonstrating that they are official, and improving search rankings." Much of the benefit here accrues to Google, which can use the "signal" represented by the presence of +1 buttons with common ownership on a brand's various pages to lift those pages in the search results. The result will be more on-target searches where brands are concerned; black-hat SEOs will have a harder time displacing a brand from prominence in a search for its own keywords. Search quality, and thus searchers' trust level in Google, should rise. Google said that when someone hits +1 on an ad in the Google Display Network, the ad itself gains the benefit of increased visibility to people in one of the Circles of the person who +1'ed. This much we guessed already. But Google also revealed that +1'ing an ad gives reflected credit to its landing page as well, so that should become more visible. Get the full story at The CMO Site