Taken from Kotaku:

"SpyParty is a two-player game that pits one person as a spy and another as a sniper. The spy player must blend in with computer-controlled characters, all of them attending a party, where the spy must smoothly complete a handful of missions (bug the ambassador, poison a drink, etc.) The sniper player gets to watch the party from outside, training their sniper scope and laser sight on any of the guests. The sniper gets one shot to ID the spy and shoot. The bullet won't miss, but they'd best be correct about who they shoot."

Here're the two most important parts:

"Everyone will compete online at first, with LAN and player server support only coming later."
"Those who pay $15 for the beta will receive all updated versions of the game, including its officially-released form. So you won't need to buy it all over again."

Linky: http://kotaku.com/5800409/spyparty-beta-starting-soon-heres-how-to-sign-up
Main site: http://www.spyparty.com/

I, for one, am already interested. May even drop the money on this soon.

Interesting concept. At first i thought it was a TF2 mod.