I've had a couple of wake up calls in my time with regards to google. Back in 2005, I started a pay section to my site when, even back then, I saw the first signs of adsense earnings starting to taper off and thought "I need other baskets for my eggs". That pay section now provides 80% of my earnings.
But, lot of traffic for that pay site comes through G, nothing horrendous but probably 50% all in all - that now has to change and have begun writing to other sites in my niche about advertising. I have only 3 main sources for the traffic to my pay site and I want that to be 5 by the end of this year, 8 by end of next year. I aim to get G's 50% down to 25/30% in 12 months. You have to diversify on today's internet. It's your responsibility as a business owner. Didn't know you were a business owner, eh? Well, that can be your wake up call. :)