After 12 weeks of socializing in select circles, Google has announced that anyone can sign up for its fledgling social network, Google Plus.

The uptake of the service now it is widely available will be crucial to the success of Google Plus, and to Google's ability to compete with Facebook as a force in social networking, and in selling more targeted ads. Google's social network was launched in June to positive reviews and considerable interest, but activity has slowed in recent weeks.

Unique features, especially the ability to target updates to different social "circles," were well received by the first rush of users. However, many of them appear to have stopped using the service, perhaps because so few of their friends also had access. Anyone can now sign up for a Google Plus account at this page.