Tamhas, but no one wants to invest in COBOL.
And yet, were someone to develop a tool which would read COBOL and spit out good code in some modern language, the market would be huge. (It has been tried, but not successfully).
The point is again a point of caution. The people making these inquiries on which this rating is based are mostly programmers, not decision makers. I have no argument with the idea that Mongo is probably winning the mind share battle in NoSQL databases, but that may or may not translate into sales. So far, they seem to be doing well, but a rating like this means almost nothing compared to actual sales figures.