It's most likely that they only took action against those players that openly support and partake in these boosts for real money. In every other case, they can't prove that there's been a real money exchange so... this just means people will be less open about these services, but they'll still keep going. There are entire companies created around these services...
I hate this as much as the next player (especially their camping of BMAH), but I get the feeling Blizzard's cracking down on it for one simple reason... they want players to buy boosts for gold, which they buy through tokens...