Maybe a couple of too strong words, but definitely a great comparison of Cassandra and Amazon DynamoDB by Jonathan Ellis (Cassandra chair and founder of DataStax):
As an engineer, it’s nice to see so many of Cassandra’s design decisions imitated by Amazon’s next-gen NoSQL product. I feel like a proud uncle! But in many important ways, Cassandra retains a firm lead in power and flexibility.
Update: this is the updated version of the comparison.
Original title and link: Cassandra and Amazon DynamoDB Comparison ( ©myNoSQL)