Joshua,
XBAPs will not be indexable by search engines for this release. We completely understand the importance of this request, and are looking into ways that we can expose the information contained within an XBAP to search engines in the future.

Linking to locations/pages within an XBAP is a related but different problem. There is no built-in support for this today either. However, you can work around the limitation by adding a bit of logic to your application that will parse an URL argument and navigate to the appropriate page specified by that argument. E.g. say my XBAP is located at http://acme.com/app.xbap, and there is a page for product 1234 inside the application. I might write some custom logic so that when a user tries to navigate to http://acme.com/app.xbap?product=1234, the application navigates to page1234.xaml, or uses 1234 as the key for a database query, etc.

We hope to have better answers to both of these questions in the future.

Thanks,
Lauren [MS]