Wilburforce - 5:01 pm on Jul 26, 2013 (gmt 0)
if their rankings improved after Google invested, that's suggestive
Not even then, really. First, you would expect the website of a Google subsidiary/affiliate to have Gooogle "best practices" applied to it, and second, you would expect a business to improve in many ways (not just Google SERPS) following investment from a multi-billion corporation.
The only thing that would show an unfair bias (as if it would make any difference) is evidence that penalty factors which apply to the rest of us were disregarded for Google subsidiaries/affiliates. We don't know what these are, and my guess is they will have been stripped out of those sites following acquisition rather than "overlooked".
How long the public will remain happy being served Google-on-a-plate remains to be seen, but if results as bad as some I have seen lately haven't shifted them, I reckon they'll go on eating it for some time yet.