I joined a company that had some investment in Basho and managed to sell Riak as the data store for a large client. It never really worked out, not enough of the SREs had be properly trained on Riak, the developers hated it because getting help and support was somewhat difficult, especially in an emergency.

In the end more and more data was offloaded to MariaDB, until one day the last remaining data couldn't justify the cost of the Riak cluster. I think we swapped out an eight node Riak cluster for two largish MariaDB database (one being a hot-standby).

For one of the other clients it was the exact same scenario, only we had been contracted in to help run the Riak cluster, which we didn't do well. Once they had migrate of it, to Oracle I think, the client left.

To me it always felt like it was just the wrong tool for that particular job. Someone really wanted to be able to jump on the NoSQL hype and sell something. They picked Riak, because it honestly looked really good, and probably was, compared to MongoDB, CouchDB or whatever else happened to float around at the time. It just wasn't the right tool for the problems it was applied to.