I remember reading some interview with the digg-staff around the Cassandra switch. I remember that the "problems" they were facing with the relational databases

I remember reading some interview with the digg-staff around the Cassandra switch. I remember that the "problems" they were facing with the relational databases were mostly bad queries designed to exhaust even a decent DB. Instead of just writing proper SQL, they wanted to replace their entire server architecture. To me that looked like a pretty bad decision and I would halfway label that a "technical problem", although it may be more related to the technical competence of the staff than anything else. Now ofcourse I can't remember where I saw it, or what the specific issues were and I'd love to revisit it. Anyone got a good memory or a link handy? :)