Zygoot - 8:14 am on Sep 12, 2012 (gmt 0)
My top years were 2005-2006, after that it only went downhill. A site that made over $150 a day at its peak is now making just $10 on a good day. Traffic is way down, but not nearly as hard as earning, and the economic boom under which AdSense flourished has been gone for years.
AdSense CPC is much lower than it used to be, and just like other posters here I've noticed that ad relevance has gone down the drain. When AdSense just came out I was amazed by how relevant the ads were, but behavioral targeting and other factors increasingly changed that. Possibly users are also becoming blind to text ads, and I think that as people get web savvier, they increasingly turn to ad blockers.
The web has also changed a lot over the last decade, new things come and go and browsing habits change. Competition is increasing, not only from big content but also from Google itself. More and more Google domains are dominating the SERPs and one of the things they've pushed hard the past year is Google+. As a content website you're pretty much forced to make an account if you don't want to end up with a disadvantage versus other sites (the whole authorship thing), and especially for localised results I'm increasingly seeing Google+ company pages (created by Google itself).
I hope to get back on the right track, otherwise I'll need to get a day job.