When the article says they envision DOTA as a service akin to Team Fortress 2, it makes me think of what they said for L4D. Then, too, they referenced Team Fortress 2.

A year later, L4D2 came out and most development shifted to that. Referencing TF2 when L4D/L4D2 are the more recent examples of the philosophy of their "service" mentality is disingenuous.