Valve, you impress me.

Logging in to Steam, I saw an ad that really impressed me: Valve is offering a copy of Portal free until the 24th to "celebrate" the introduction of steam for the Mac. Personally, I see it as an awesome business decision. Trying to get people to sign up for a service they don't currently have need for is difficult. Offer them a free game, and it gets a lot easier to bring people in. Once in, they'll see the ads, and might be tempted to buy more. This will dramatically increase Steam's popularity on the Mac, which is vital to both its sales and success on the platform. I'm not accustomed to seeing this much intelligence from game companies.