AZ open access
Instead of Diamond OA (as mentioned in Tim Gowers very interesting “Why I’ve also joined the good guys“) I suggest that a better and inspiring name for this yet mysterious idea if epijournals would be
AZ open access
or open access from A to Z. There is another, better justification for this name, see the end of the post!
Diamond and Gold names just betray that many people don’t get the idea that in the age of the net is not good to base one business model on the SCARCITY OF GOODS. Gold and diamonds are valuable because they are scarce. Information, on the contrary, is abundant and it thrives from being shared. Google got it, for example, they are not doing bad, right? Therefore, why base the business publishing model on the idea of making the information scarce, in order to have value? You already have value, because value itself is just a kind of carrier of information.
The name AZ OA is a tribute. It means:
Aaron SwartZ Open Access.

The value of information is in its relevance to the particular question or problem that one has at the moment. Sifting through the universe of possibilities is not easy…
You are right. In order to find out if this piece of information is relevant for that question, one needs access to information (through sharing, right?). Or, making the information artificially scarce it lowers the value, as defined in your comment.