Google already has the Google Checkout payment system and its Products search tapping into all sorts of online merchants. Google could theoretically tie both services into Google+ for businesses, enabling a company to link its payment service to a backend database of products within Google's ecosystem, rather than sending shoppers off to PayPal.

Facebook Pages, by contrast, enables SMBs to build pages with e-commerce using third-party tools like TabJuice, which costs $20 a month. Most other services for adding shopping to a Facebook Page cost many thousands of dollars. But Facebook is lightweight. It focuses on content sharing and communication among "friends," leaving product databases and payment methods to other services to handle. The closest thing you could say it has approaching a market is Facebook Marketplace, a would-be Cragistlist rival that really hasn't gained traction.

Business Websites

Google has Sites, which is limited, really more for team projects and minor intranets than for rich, public business websites. Similarly, the layouts of Facebook Pages are constrained by that site's layout. To dress up your Facebook Page, you generally need to to do so, or seek a third-party tool such as Shortstack to help.

Google would be smart to let businesses use the tried-and-true programming languages, such as HTML and CSS, in addition to drag-and-drop design templates, to doll up their Google+ presence. However, the search giant may very well limit the way a business appears on Google+ to the current Circles constraints of that service. But by harnessing its Blogger publishing platform, Google could enable users to say far more than the short text bursts in Facebook's stream of updates can.