You're probably thinking about this as "instances of NoSQL services replacing RDBMS installations" but that's putting the playing field in the wrong place. Look at it as a venn diagram. There are 3 important zones: the zone where RDBMS excels; the zone where RDBMS and NoSQL compete and one or the other may be preferable depending on circumstances; and the zone where RDBMS never makes sense. You're looking at the field as the first two zones, Yegge is looking at all three zones.

Which means that you're missing things like caching engines, such as memcached, and other services which are not replacing an RDBMS but filling a different niche, which are widely deployed in industry.