And we have a winner! Congrats, Ryan. Your copy of Yahoo! Hacks will be on its way later today. Thanks to everyone who played!

The answer I was looking for: February 2005. You can read more about this moment in history here, here, here (my post), or here. And if you already have Yahoo! Hacks you'll find the answer on page xiv in the Preface. This launch was a turning-point in my perception of Yahoo!, and of course that release kicked off an entire year of suprising announcements from Yahoo! including acquiring Flickr, launching Yahoo! 360, launching My Web, and acquiring upcoming and del.icio.us among many others.