This comes from the Creating Passionate Users blog. Kathy Sierra is highligting some of the events at SXSW.

From Jason Fried of 37signals:

"Make it up as you go along. You're in a much better place to make a decision when you're in it, than when you're planning."

When questioned about whether the 'no-planning' notion was a nice utopian vision, but not practical in larger development worlds:

"I think it is MORE utopian to think you can plan everything in advance."

"We don't use functional specs... we use stories."

This is a scary concept which I think needs to be embraced. I don't believe he intends for you to discard planning completely, but to tailor your development strategy to allow the project to evolve and change as you progress. Not much more to say at this point... I'm still reading some materials that is helping me form an opinion - which I need to reconcile with my own experience.