I understand this can be done through support for the moment. Yet, the flexibility and responsiveness won't be the same as if the admin could do it on its own.
This is a mandatory feature in ordert to suceed in B2C industies such as e-commerce. For instance to be able to manage shopping carts.
This would be huge for leads and forms (like capturing RSVP details and the like). Unfortunately, from what I understand, custom objects can only be accessed through the SOAP API and not the GUI. As someone noted earlier in the thread: is this on the roadmap?