Google’s latest foray into social networking is a must-win situation. As Jason illustrated last week, the world is watching to see how the search giant uses social data — particularly their own from Google+ — to adjust search engine rankings. With Microsoft working with Facebook to allow Bing results to include social data from its 700 million-plus users, Google+ is a make-or-break to hold on to SEO dominance.

But it’s not just how Google uses the social information it gleans that matters. It’s how many people will use it. My guess is that 50 million users or more won’t even be critical mass. It will take many more people and Google’s careful use of the social data to be successful.