Interesting post on the memcached mailing list about how Digg are using Memcached for session storage. Memcached is intended as a caching layer, but after their session database crashed, they simply went with using Memcached for session storage period.
The new Geograph setup should wind up with around 10GB of memcached space across 5 nodes, and I was hoping to do something similar for session storage. It sounds like the Digg system barely broke a sweat doing this as their memcached nodes were already being hit much harder by their main application.
If it’s good enough for Digg, it’s good enough for Geograph!