Foursquare, a mobile-based startup that lets people ‘check in’ at bars, restaurants and other places through their smartphones, has raised US$20 million from a group of venture capitalists to help fuel its expansion, according to The Wall Street Journal. The investment was led by Silicon Valley venture capital firm Andreessen Horowitz, a year-old firm started by Internet executives Marc Andreessen and Ben Horowitz. The fast-growing company was valued at US$95 million before the investment, up from US$6 million when it last raised money in September.