Foursquare, the location-based mobile application, announced yesterday it scored a fat $20 million investment and a new funding partner, Andreessen Horowitz, the VC co-founded by Netscape whiz kid Marc Andreessen. What will the loss-making start-up look like now that it has actual money in the bank?

First up, a new office! Yes, the company will be using the capital to improve its back-end, primarily by purchasing more equipment, hiring more engineers, and getting a sweet office in New York City. Not bad for a company that was based round a kitchen table a year ago.

But the real gain is the company’s newly minted legitimacy (an 8-figure investment will do that) as a technological innovator. We’ve written on the geo-based possibilities in general before, noting, in particular, the impact it will have on the retail sector. But now with ample backing from the likes of Marc Andreessen, a man who knows a thing or two about big tech bets, Foursquare has the funds to expand its current 1.7 million user base and streamline the capabilities of its service for commercial advertising. In an excited blog post, Andreessen noted:

Users have been so excited about the product that they’ve actually been signing up local businesses to run promotions for Foursquare’s mayors and active users… and over 10,000 businesses are currently working with Foursquare to build customer loyalty and drive traffic.

One of those 10,000 businesses is Starbucks, which started a loyalty program in the U.S. for avid users mayors. Another isWhole Foods. We haven’t seen much from European retailers, but a fresh funding round could make that happen, and jump-start the social shopping sector here.

As Foursquare CEO Dennis Crowley says, “we’re just getting started.”