From my point of view, there are a number of things that are "unfinished" about the site and they don't all have to do with technology. Here are a few.
1) Figuring out the right price to charge for the squares is something that probably would benefit from some more thought.
2) There buying process is pretty rough and there is very little text to reassure the customer as they are going through the checkout process.
3) The incentive structure is very rudimentary. People have to get it in order for them to see the value, and that takes a bit of imagination. The initial sweep of squares seem to be purchased from either the "it would be neat if this takes off" or the "i have some extra money in my paypal account" people. I could spend a lot more time working out this part of the site.
4) The design is, heh, rough.
As for the technology, I'm happy to go into it in more details but I'll summarize here for brevity:
- Ruby on Rails 3, hosted on the free Heroku cloud stack (Ruby, PGSQL)
- Paypal handles the payment processing and invoicing
- Basic REST Twitter API for pulling down the twitter account details
- Twitter OAuth is used to handle the optional account signup
- Twitter's S3 account serves up the avatars, although I'll probably have to change that
- Each purchased square is assigned a bit.ly URL that I use for tracking clicks and surfacing statistics to the owner of the square
- Google Analytics for the tracking
- Page caching is used for each of the pages to minimize server load
Total Cost: $0