"Apollo placed a curse on her so that no one would ever believe her
predictions. "
http://en.wikipedia.org/wiki/Cassandra

So it will never scale

http://techcrunch.com/2010/09/07/digg-struggles-vp-engineering-door/

Digg was originally built on the tried-and-true LAMP stack (Linux,
Apache, MySQL, PHP) of open-source technologies, but it was straining
under the load of Digg’s traffic. Replacing MySQL with Cassandra was
supposed to help fix that. It came with its own set of larger problems
instead.


this i saw in the field : you must add more people to keep the site on
with oodbs or tree based storages