Filtering Repeater Items Based On User Status / Role?

I have a tricky requirement where I need to categorise documents attached to a product, available for download, based on the status of the user viewing the product. I.e. my site displays a list of products, clicking on one displays a product details page, and this page includes a list a documents related to the product, such as data sheets, user manuals, etc.

I have been asked to group documents into three classes of availability, v.i.z. those available freely to all users, including anonymous; those available to logged on users; and those available to anonymous users that provide contact information before downloading the document, presumably to boost sales leads.

The anonymous and logged on availabilities are quite easy, but the third seems a bit tricky to me. My first question is, is there a way I can filter documents for only logged on users without hooking into ItemDataBound or something, and my second question is, what is recommended for the case where a user must supply contact information to download a document?

In the second question, it has crossed my mind to actually register the user, but without them having to visit the new user registration page, and then I have role based filtering of documents. Currently the new user registration process automatically adds the Member role to all new users. Users I register 'quietly', just so they can download a document, wont be assigned the Member role, distinguishing them from normally logged on members.