Perhaps I'm dating myself a bit here, but there was a time when there was no such thing as an "e-commerce app" and no wi-fi to eavesdrop on. Black hat hacking has evolved also, so although some techniques have always been possible, new vectors have opened up over time as they are discovered and disseminated, and I would suggest the corresponding knowledge burden needed to enter the arms race for a developer is higher now. Also, the tools have evolved in such a way that the barrier to entry is lower and lower. For example, FireSheep.