Five Reasons Why a Pay Per Click Recession Looms [micropersuasion.com]
Pay per click advertising generally suffers from low trust from advertisers as it is a easy target for fraudsters to generate fraudulent clicks. Be it as it may, in regards to different types of advertising, despite it's popularity going up or down, it's still here to stay.
If things stay the same and with the rise of web 2.0, affiliate marketing, behavioral targetting, etc, of course PPC recession is bound to happen as we're constantly generating innovative and targeted ways to advertise.
Yet with the increase of small businesses, rise of more businesses venturing into the internet, throw in India and China and you see that there's still a lot more ground to grow before PPC market truely matures and starts to die of.
But also, affiliate marketing and newer more effective forms of advertising that focuses on results will grow alot faster.