OP_RETURN can be used to store references to external resources, say for example very long meta transactions that don't fit into 40 byte, an asset contract or whatever. The storage pointed to could be a website which lists something like (for the sake of an example), a side chain or a P2P structure like a DHT. To my knowledge this was discussed several times, but never tested on a broader scale.
I've started researching the DHT myself, dexX7. However, a side-chain structure like a DHT would require a good understanding of the particular DHT algorithms that would be a best fit for Counterparty or even Mastercoin or any other possible bitcoin layered protocol.
An interesting introduction to the Chord and Kademilia algorithms is by a bitcoin developer here:
http://offthelip.org/?p=149Do you have any resources that you've looked at as well?