Google is doing more text ad testing in the last month than the last 5 years. Every time I check my site it's something different. Not really why? The text ads seem to get the highest CTR and they seem to forcing image/rich media on us - so it's surprising to me to see so much text ads testing when display is the future of AdSense.
They can do all the testing they want, cause I decided to call it quits by the end of the year, if not before. It's just not worth running if they make these changes and cause the earnings to go down the tubes.