Google was handy because their policies weren't overly restrictive - perhaps this is what sunk the digital goods api... Stripe is wonderfully easy to set up but doesn't allow integration for certain types of app e.g. telecoms (I understand that this is because of retrictions banks have placed on them).

Trustworthy Bitcoin payment processors are tricky to find. The stripe approach to this does give the lowest amount of customer friction imo (i.e. options to convert usd to btc on the spot) but the market restrictions and the beta status make it a non starter for now.

I'd be curious to know what prompted this retirement. Having moved from Google Checkout to Google Wallet, it's more than a little frustratingt. The Wallet customer experience was pretty good and the integration process was fairly simple. It's a shame to lose this and lose yet more faith in Google to keep their services alive.

They're only shutting down payment for digital goods, so I'm guessing it has something to do with fraud and risk.

Payment for digital goods is the only payment that's left from the Checkout shutdown (other than Android).

Instant Buy is for non-digital goods.

Instant Buy doesn't actually process payments, it gives you a virtual card and then you need to use your own credit card processor.

Products such as these already exist and produce around 30-75 liters/day [1].

[1] http://www.water-gen.com/product-water-generator.html and

If you use Mendeley for organising your papers check out KinSync.com. Pretty good for this.