diberry - 3:10 pm on May 30, 2012 (gmt 0)
4. On good days, the traffic source countries have a higher percentage from the US and UK. On bad days, a high percentage of traffic comes from India.
See, this is the sort of detail that makes it so hard to doubt traffic shaping. What else but search could cause this effect? I can't think of anything.
2. The traffic share to the free pages has increased, and non-free pages decreased.
1. Google has perhaps weighted my site as having a high percentage of free content and sends a larger proportion of non-paying users my way.
It seems to be that offering free and non-free stuff is a good way to build trust in readers. I expect at least some freebies even from major brands that are nothing but shopping sites. So it doesn't make sense to me that Google would be incorrectly classifying you as a content site.
There's another possibility. What if Google is just looking at particularly lucrative Adsense keyphrases, and finding ways to cherry pick who it sends free traffic for that phrase, so as to keep people buying Adsense? When we speculate about why Google would bother with traffic shaping, it's hard for me to imagine another reason. I can't see that it improves user experience. Therefore, it's got to improve something from Google's perspective, and Adsense is most likely.
If that's the case, splitting your site would not help, because all Google wants is for you to buy Adwords.
Just some thoughts. I'm not saying any of this is correct, just offering it up.