This stood out, negatively:

Since Cassandra uses Apache Thrift as the default RPC mechanism, exposing the Thrift layer to any non-controlled data can be dangerous. We use firewalls on our nodes to make sure our Thrift ports are only exposed to a very small set of machines, because even just telneting into the port and typing "hello" can cause the JVM to OOM.

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I use Redis and heavily guard its telnetable port, but it doesn't OOM. This issue should have been fixed before public release, imo. You wouldn't want something as simple and common as a port scan to shutdown your data layer.