Dan gave a brief explanation of "blitcoin" on the forums:
"As reported, I've got a BitCoin deanonymization mechanism. It's not complicated.
Connect to every node in the cloud, discoverable via sweeping/IRC/get_peers messages. The first IP to consistently relay transactions for a given identity, is the given identity.
Of course the entire BitCoin cloud doesn't allow inbound connections (although you can do rather evil stuff with UPNP to force that open too). But this isn't a problem -- there's only about 3000 to 8000 IPs that are BitCoin nodes that accept inbound connections. Since everyone else depends on them, you just need to create your own mass cluster of IPs that are a decent chunk of the P2P network. Nodes on average have seven outbound connections, so it should take only a few hundred unique to be one of the first-hop peers even for the outbound-only set."
... so it is a de-anonymize-via IP address not de-anonymize-via Bitcoin address. And might go partway to explaining why we're having trouble with network connectivity...