I liked the article, but I'm confused: RoR hasn't taken over the world?
Job offers on Dice.com:
Java: 16837
Javascript: 10161
C#: 8011
Ruby: 1707
Ruby on Rails: 679
Scala: 82
Market share on Tiobe:
Java (#1): 18.5%
C (#2): 16.27%
Ruby (#11): 1.48%
Scala: not in the top 20
So, the article is right: Ruby on Rails is still quite niche.
(can't believe HN won't let me format this comment better than that)
Ruby on Rails would be there as well if it were mainstream.