Wary.
Don't forget that SatoshiDice started in April 2012 and kept growing until it was doing about 70% of the volume a year later. Each bet was a transaction pair in the blockchain, and some people were even using bots! Fee increases and SD internalization got rid of most of its volume by about July 2013. So the growth since then is much more of a "real world" business flow. Still, some spam-like volume coming from betting sites.