How does blockchain.info get their info? My intuition tells me that they have a modified client that reads and processes the blockchain (either directly from the network as it comes in or from the raw files on disk) and stores the various data and relationships in a database.
I'm also guessing that they may use the RPC interface for the standard bitcoind to do simple things like getdifficulty() or getblockcount() quikly.
Can anyone confirm this? Any ideas?