A detailed WebmasterWorld thread has dozens of complaints from Google AdSense publishers about the quality of the ads.
In short, publishers are noticing that the ads are repeating themselves multiple times on the same page and the ads are less relevant and sometimes borderline spammy. Typically, Google does a relatively good job with the quality of AdSense ads. But it seems like something went out the window recently, at least according to these publishers in the thread.
AdSenseAdvisor did confirm that he/she spoke with the right people at Google about this. AdSenseAdvisor said:
After talking to AWA and others, I can tell you that your specific concerns are being heard by the right people at Google.
I won't be able to say anything more than that on this subject, but please know that the "no comment" is coming from the the right people.