ok, back home and exhausted. lots been said here...
Rupert, I think you will need to see it implemented, because I think there are some misconceptions. Access is just like any other OpenID or OAuth method of identification/authentification.... it's your customer and you will end up with whatever information the customer will give you... Access just fills out some of needed fields for shipping, but more importantly offers frictionless purchase option... no cumbersome registration process only to have to fill out billing info, etc.... login with existing U/P and 'click buy', done. difference is about 5 minutes on a desktop and most likely no sale on a mobile.
Leona, I hear you but I think this is the next 'best of breed' solution for merchants with lots of products. It also is pretty easy to use for how powerful it is. Imagine a platform for developers to build modules you can plugin to customize the store to your needs. That all of your products can be imported and categorized in seconds, then from there exported into ebay, and all your ads generated in Google, Facebook, etc., automatically (assuming you already opened up accounts, etc.). Once you start doing any business, you have epic stats that are fully integrated with your adwords campaigns, emails, etc. so you can see when you are hitting diminishing returns and focus your spend where it could be better used. Combine that with lower friction registration and checkout and you start to get the drift of what I'm talking about... if you have 40,000 products and you want to switch to a new enterprise solution, you'd couldn't find a better, more integrated solution on the market, and you'd never be able to afford to replicate the system by your self... once you see it you'll understand.
In short, it allows business owners to just focus on business and not technology and I think it's a game changer in that space.