updated 11:35 pm EDT, Wed June 29, 2011
Anyone with an e-mail address can be invited
(Update: temporarily shut down) Google is now allowing early adopters of its Google+ social network to invite others, via an icon on the bottom right of the main Google+ screen. Users can add anyone with an e-mail address to their Circles and share content with them, which includes an automatic invitation to join the service.
A rapid buildup of users is crucial to Google's challenge to Facebook as the dominant social service on the web. The social service creates a persistent toolbar that appears on any Google-related site (such as Picasa, Google Maps, GMail and so forth) that provides access not only to Google's other services but a friend-gathering option called Circles, where users build links to contacts, and the company's equivalent to Facebook's "Like" button with the "+1" tag next to links on Google-related pages (such as photo galleries and search results).
Google has previously criticized Facebook for not sharing more data collected about its users. Google+ could be simply Google's way of getting around the problem of collecting even more intimate usage data via social activity while unifying their diverse services to make them more accessible to users.
The service also makes it easier for members to video chat with up to nine others (bandwidth permitting) and also features group messages similar to Google's unsuccessful previous attempt at social collaboration, Google Wave. Mobile OS users on Android have a native mobile version of the service available now, while iOS users can access a mobile-friendly HTML5 web page until the native iOS app is approved.
Update: Google's Vic Gundotra said on Google+ that invites have already if temporarily been closed down.
"We've shut down invite mechanism for the night," he said. "Insane demand. We need to do this carefully, and in a controlled way."