Is there by chance a registration module which replicates the form that shows above the activity stream when logged out?
I love the layout but don't like having only the activity stream as an option below it, I've turned it off for now and used the components anywhere module to pull in the marketplace but its causing some odd behavior with the links.
What I'm thinking might work better is if that form is in a module I could just publish it above the marketplace and only show it to guests.