We're not marking up the exchange rate. 0.5% is the only fee.

Awesome work! I've been trying to push bitcoin at our company as a form of payment, we use Stripe already, so this will make it easier.

Inherent to Stripe processing BTC is the fact that you are now a foreign exchange broker. Here's a small sample of why you're going to have to do a lot better than "we only charge 0.5%" to convince me that adding FX risk into my payment processing stack is a good idea:

http://www.bloombergview.com/articles/2014-11-12/banks-manip...

http://www.bloombergview.com/articles/2015-02-09/banks-will-...

And that's just from the last three months, in an arena that is already heavily regulated by the SEC.

Hm? As a business selling with Stripe, you won't be taking any FX risk. You request $20, and you receive $20 - 0.5%.

I am a huge fan of Matt Levine's work, but the articles you reference are about banks who participate in the FX markets, which is... different.

(Relevant disclosure: I work at Stripe.)

Marking it up from what? There isn't really a canonical exchange rate.

That cost would be borne by the customer, won't it? I guess that's still in some sense a fee from the Stripe vendor's perspective, because the Bitcoin price will be higher for the customer and thus the quantity demanded will be lower than it would be with the vendor's USD sticker price.