A solution to the “Tragedy of the Commons” problem in Bitcoin ?

[casascius]

I have occasionally proposed that miners could offer value-added services for transactions that include fees beyond a certain threshold.

For example, miners at large could offer a UDP datagram-based real-time acknowledgment of having heard a transaction and an informal commitment that the transaction is not a double-spend.  This would enable instant transactions with a smaller attack footprint when it comes to double-spends.  If this were built into mining software, it would become a no-brainer and essentially a de-facto feature of the network.