There are so many stories of unintended negative consequences in development, whether it's dams and resettlement, or the Green Revolution as well as stories of efforts that had no impact, that it gives me real pleasure to talk about intiatives that had unintended positive consequences. One is an old story, the other one far newer, at least to me.
The old story is about the story of Tripod and Ethan Zuckerman. Tripod, as you can read on Ethan's page, was originally intended as a edited content site but took off as a homepage site (and was eventually sold to Lycos) when Ethan and his techie team were fiddling around with a DIY homepage, made it available to the readers of their "content site" and discovered one day that they were about to exceed their bandwidth limits. When they investigated what was causing the massive traffic pileup, it turned out that far more people than they had ever expected had decided to set up their own homepages.
The new story is one that I read on a newly discovered blog of Christine Herron's. Although GlobalGiving is an investee of the Omidyar Network, I hadn't come across Christine's name until another friend started asking me advice on how to find the right people at O/net, and asked me about her. A little googling, and I found Christine's profile on O/neet, but better still her blog, and the wonderful story about Flickr. You should read more about it on Christine's blog, but in a nutshell Flickr intended to build an online multiplayer game, and the photo sharing function was just one of the tools for the game. But because they intended to be a game and based in an online community, they made a point of welcoming new people, teaching them how to navigate the site, etc. Although I still believe Flickr's tagging technology is a killer app and should be credited with their amazing popularity, I am also psyched to hear about the unintended consequence of their original intent to build an online game. And at least they got part of what they were aiming for--a real community.