Edit Mode Permissions and adding blocks

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Does anybody know if you can control what blocks a user will see when adding new blocks in edit mode.

To give you an overview of the situation I am working on a social network add-on and was thinking of using the edit mode to let users position data blocks but i would rather them not have access to all available blocks.

I would be very much interested in anyone's opinion on a solution.

Regards Frazer

frizzleb