Wow, top story on HN. Thanks, folks! I wanted to call out a number of things I glossed over to see if it's worth doing a follow up or seventeen:

  * Personal guarantee.  Most merchant account providers require a personal guarantee.  I signed one for Dawdle.com, but I never would again, even if it costs me more.
  * Recurring billing.  There are a number of startups focused here, including Recurly, Chargify, Spreedly, and CheddarGetter.
  * PCI compliance.  The physical access tenet makes it technically impossible to be compliant if you're using any cloud hosting provider for e-commerce; in reality, almost no one is PCI compliant.
  * Gateways.  There are a bunch.  ActiveMerchant (Ruby gem open sourced by the good folks at Shopify) can do basic handshakes with most.  There isn't an AM equivalent for Python, PHP, or other common languages that I know of.
  * Processors.  First Data ostensibly processes 75% of credit cards in the U.S.  This is a more academic topic than the others, but it's terribly interesting if you want to understand why online payments are the clusterfuck they are.
  * Chargebacks.  You'll almost never win one.
  * AVS and CVV.  They protect you, but goddamn, are they expensive to process.  AVS can sometimes cost you a dime (or more!) every time you check a card - and it rarely works on non-U.S. addresses (and American Express often fucks up apartment addresses even within the U.S.).
  * Vaults versus reference transactions.  Reference transactions are an elegant way to handle credit card data, but they lock you into the gateway.  Vaults give you portability, but those providers are always more expensive than the ref tranx folks.