We think it was because of the economic crisis. The restaurant sector was hit pretty hard and that probably caused a lot of companies to stop advertising.
The revenue is now back to it's old levels, but it stayed that way for 6-7 months.
We started a program that allowed restaurants to advertise directly with us. Made it very easy to try by not having any contracts and being a lot cheaper than our competitors. We got someone to do sales on a commission-only basis. He was so good (~ 70% of the restaurants he calls become a customer) that he is now a partner.
We also added affiliate links to sites where you can order food online, make reservations, etc.
Anecdotally, the Adsense revenue for my old startup also collapsed in late 2008/early 2009, from a peak of $1.00 cpm to $0.17 for exactly the same ad and roughly the same mix of traffic.
We went through a similar transition, although we started ours much earlier. If you make your page full of ads, you should be able to scrape together $1 cpm pretty easily, but sell extra content to a good game on that same page and it'll yield $10+ cpm - my latest game is a $50 cpm. That's a pretty serious difference!
The revenue is now back to it's old levels, but it stayed that way for 6-7 months.
We started a program that allowed restaurants to advertise directly with us. Made it very easy to try by not having any contracts and being a lot cheaper than our competitors. We got someone to do sales on a commission-only basis. He was so good (~ 70% of the restaurants he calls become a customer) that he is now a partner.
We also added affiliate links to sites where you can order food online, make reservations, etc.