I'm adding a Lead form to a Site.com page, similar to this blog post by Joe Morse.
I am able to select the Lead object from the form connection picklist when dragging the form on to the page and I am able to hide the Owner Id field. In order to choose the Lead in the form connection picklist the Site Guest User's profile must have Create permissions on the Lead.
The problem is that when I try to specify a Fixed Value default value for the Lead owner I do NOT see the Site Guest User as an option in the picklist of possible owners. The only users that are available in the picklist are customer portal users.
How is the list of Users that is populated in the picklist of possible default Lead owners determined? Is it something more than just having the Create permission on the Lead object?