Tech news from around the web:

Google+ is now open to the public, the Los Angeles Times reports. After 12 weeks of field trials, the social network is still technically in a ‘beta stage’ however, with nine new features being added this week and more planned for the future.

Location-based app Foursquare has just clocked up a billion check-ins, says TechCrunch. On top of this, Foursquare has launched a new version of its mobile app for the iPhone and Android handsets. Read more

Marc Andreessen is on a roll. Earlier this month he raised a $300m venture capital fund with his business partner, Ben Horowitz. Now Ning, the social networking startup he co-founded, has raised $15m from Lightspeed Venture Partners at a whopping $750m valuation, according to All Things Digital.

Valuing Ning at $750m seems more than generous, considering the company has never said it is profitable. Even before the economic crisis, these would have been favourable terms. Slide, which makes applications for social networks, last January raised money at a $550 valuation, while LinkedIn, a social network for professionals, got a $1bn valuation last JuneRead more