Details on Yahoo's distributed database

The good folks at Yahoo Research published a paper at VLDB 2008, "PNUTS: Yahoo!'s Hosted Data Serving Platform" (PDF), that has juicy details on the massively distributed database behind most of Yahoo's web applications. An excerpt:We describe PNUTS, a massively parallel and geographically distributed database system for Yahoo!'s web applications. The foremost requirements of web applications are

[rawwell]

"First, the system is layered on top of the guarantees of a reliable pub-sub message broker which acts "both as our replacement for a redo log and our replication mechanism." I have to wonder if the choice to not build these pieces of the database themselves could lead to missed opportunities for im