I hope you don't mind some feedback. The LEARN MORE button is visually broken (I assume). When I want to learn more I don't actually learn more. I really have no idea how your service works. Then there is the issue of non-existing SSL which is a big no (even though it might not be needed for this service) for any kind of payment provider. And of course the twitter login. Though I understand you don't want to mess with your own account system.
SSL is unnecessary for accepting Bitcoin payments, there's no reason at all for SSL to be used on this site.
What if I MITM the site and replace the seller's address with mine?
that typically would be a concern, but our first version is built only with a Coinbase integration, and all payments are handle through their merchant services and their payment iframes. Once we implement our own payments we will have to handle this appropriately.
What if I replace the iFrame URL with an URL of a cloned page? How can the user be sure that it's really Coinbase's form?
Looks good.. it seems to be doing something very similar to Coinbounce https://www.coinbounce.com/ which is what i've been using to sell a couple of stuff for Bitcoin
It is not working? or it is twitter login only? (i use http://satoshibox.com/ working well so far, without login or whatever)
yup, it is currently twitter login only, there will be other login options soon of course. haven't seen satoshibox.com, they are keeping it nice and simple