If you are using MongoDB in a way that is similar to the way you would have used a SQL DB you are probably doing something wrong. Specifically, you are trying to place normalized data in a database designed for denormalization.
As a startup, it behooves them to attack the low-end database market, but I suspect they've found that the primary market for a highly scalable low-end database lies on the web, but that market has chosen to go cheap-and-dirty with NoSQL. So now they're in the middle ground between fast-and-and-loose-and-free and my-enterprise-uses-Oracle.
I think a lot of web development is of a highly speculative, winner-take-all sort, so devs. want to be as cheap as possible until they win the web lottery. For all the flaws of NoSQL, software only solutions do allow developers to make very efficient use of their hardware by running multiple services on the same machine, or run them in the cloud. Once they hit the jackpot, they can afford to either go Oracle, hire software developers to work around deficiencies in their data store (e.g. Facebook), or use a data store from Amazon or Google or Microsoft.
That's a shame, because I think Clustrix is ultimately the right approach. The web has a history of doing the shittiest-and-easiest thing first (ColdFusion, anyone?) only to repent years later to the second-shittiest solution. Rinse, repeat.
Looking at a coarse, "they want money from people" granularity, the target market (people who need a database) may be similar. If we look closer, however, the target market has, more or less, two segments:
One is at the product-for-free pricepoint, where you make your money either by selling additional services (e.g. 10gen with MongoDB, Basho with Riak, MontyProgram with MariaDB and MySQL) or upselling them to an enterprise version (e.g. IBM's DB2 Express-C, whose 2GB limitation makes it perfect to hook people on a workload they would use MySQL for, Franz' AllegroStore, OpenLink's Virtuoso open source edition).
The try-our-product-for-free method means that all the cheap-and-dirty-folks have something in their grubby fingers to build the next blog, mom-and-pop online store, or whatever. The folks with actual money to spend can lower their initial risk by trying out a couple of different databases to see which one fits best, without even having to ask. Only when they're actually happy with what they've got they're going to fork over the cash.
The next tier is the "we'll have to qualify you before we send our sales engineer" tier where you play with Oracle and IBM, or Greenplum and Vertica, because your prospective customers already know that your product is good enough.
There's no real space in-between. Either you have an engineer with good knowledge but no discretionary budget (whose chooses something appropriate for the task, after testing on a real workload, and makes the DB a non-topic for everyone else), in which case a comparison that people cannot replicate is not going to help you, or you have a high-level decision taker with budget power but no time to try things out or risk a couple thousand on a startup that may have gone bancrupt when he most cares about it. This latter category will be thoroughly unimpressed by any benchmark that is not the TPC-C or similar. No lottery whatsoever involved, these are the rules of enterprise spending.
BTW, calling ColdFusion and PHP (which were a far superior alternative to writing Perl CGI scripts without templating or any kind of library support) shitty and Clustrix "the right approach" is something for which people in 2024 will just laugh at you, even if Clustrix manages to do extremely well end ends up as the second-shittiest solution to a common problem.
Note that I am a huge fan of MongoDB and using it in production since the 1.4 something release.
MongoDB claims to support both. So does Clustrix. I'm comparing both claims.
A job is a job and data is data. Attacking the interface doesn't seem entirely fair. SQL is used with a good number of non-RDBMS. Should it really matter if my interface is a QBE JSON document, a JavaScript function, or a SQL procedure? That seems like one of the least important concerns.