Some of the NoSQL solutions take durability very seriously, some put it second to looking good in benchmarks. NoSQL is about choice, and the most durable of the NoSQL stores are more durable than many of the venerable relational databases.

For instances, what CouchDB treated as a major bug, is the accepted behavior of many relational databases. (Eg, data isn't lost, but must be recovered via a long-running process should there be an uncontrolled shtudown.)

Riak and Cassandra also have modes that treat durability as paramount, and give you better assurances than MySQL or even commercial RDBMS products.