Quote from: Perlover on July 27, 2014, 08:56:22 PM

So in future the Bitcoin Core can compress the local blockchain and eliminate all old spent transactions.

Yes but it is important to consider the impact that will have on other nodes. The current protocol only supports relaying "full blocks" so if your node only contained pruned blocks then you would not be able to support the bootstrapping of other nodes. In essence you would no longer be a full node. You would internally have the security of a full node however you would appear more like an SPV (lite) node to other nodes on the network.

What is needed is a more robust set of internode messages so that nodes can request and relay pruned blocks. Also this has less of an impact than you might imagine. Today your node doesn't really "use" blocks beyond building the UTXO. Your node stores them for archival purposes (and to bootstrap other nodes) but the blocks are only used to build and update the UTXO. All validation of new txns and blocks is done against the UTXO. The UTXO is much smaller than the blockchain (0.4 GB vs 20 GB) and it is the more critical resource. Pruning blocks won't change the performance, size, or resource requirements of the UTXO.