Left 4 Dead 2 - Dead Air campaign will be released early if enough people beat Cold Stream

In a post on the Left 4 Dead blog Valve have announced that if 20,000 people earn the Stream Crosser achievement (for finishing the Cold Stream campaign) by next Sunday they'll release the Left 4 Dead 2 version of original Left 4 Dead campaign Dead Air early on July 22nd.

Valve are describing this an an extension of their usual testing process, where the whole company gets a chance to bug test a new game shortly before release and prizes are given out. Cold Stream has been developed publicly, so this time we get a taste of what the Valve testing process is like.