[pcarmichael]

MongoDB was ruled out because auto-sharding is still alpha (though it should be out of alpha soon, I'd prefer to wait and see what the community experience is with it first.)

Between Cassandra and Riak, I chose Cassandra because it can run on windows while Riak cannot. I needed it for a data store for some cluster computing work I'm doing, but for various reasons needed my test environment to be windows only. I think I can get rid of that restriction; perhaps benchmarking Riak vs. Cassandra for my particular use case is in order.