You've got to admire this. Everything in that post makes complete sense and is stuff I've read time and time again. For some reason, though, I keep falling into the trap of trying to perfect everything I make before I let anyone else see it.
Just curious, what were the initial assumptions proven wrong by their 3 week old MVP? Would be awesome if the founders jumped in, there's not much backstory on the blog.
Oh, so much. We've completely rebuilt how we do starting prices, we've tried flash sales (everything would queue up until a certain time of day), we didn't think we needed Paypal support, we didn't have granular notification settings so you couldn't initially "follow" a specific product, guaranteed offers have been completely reimplemented 2 or 3 times, etc.
The bottom line, something we really learned from Yardsale, is no matter what you build, the perfect product, you'll end up discovering you built the wrong thing. The longer you spend on your beta, the more costly deep iterations become -- design assets, polish, etc. all are very expensive.
We started out with I think a 2 wk spec, which actually took 3 wks to build, and followed up by restricting every new feature to a 2 day spec, including big things like user-to-user payments. This changes how you think about these features. Suddenly you realize you don't need ACH integration, you can mail checks until you hit some scale where an intern can't handle it any more, etc.
PS - Shout out to Scribd, and the Parse founders, who've made an art of this kind of development.