Everyone should start to get familiar with Foursquare. Because Ashton Kutcher supports it. And any social media site Ashton supports becomes either our latest obsession (Twitter) or guilty pleasure (Chatroulette). Kutcher partied with the plebs at the SXSWi Foursquare party.

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When word got out that Ashton would make an appearance at the party, fest-goers ran to Cedar Street Courtyard with phones in hand, ready and waiting to twitpic and tweet.

Even though Kutcher stuck to the VIP area for most of the night, he trekked out to sign the obligatory autographs and pose for pictures (sarcastic poses intact) with the tech geeks whose night he just made.

Guests spent the night snacking on Popchips, hydrating with Vitamin Water and freaking out on their Blackberrys.

[All photos via Nick McGlynn]