ehgee - 4:44 am on Apr 13, 2012 (gmt 0)
One thing I don't feel is google being "naive".
That being said, it would be foolish to try and game the snippet system or putting it up where it's not relevant. There are simply too many ways that could be used (by google) to detect if these were being manipulated - bounce rate pre&post snippet; correlation of snippet reviews with reviews on google checkout / reseller ratings; rate of growth in reviews as a % of web page traffic, etc. etc.). For all you know, encouraging snippets may be a way of having website owners use Google checkout (as they can give snippet sites that "also" use Google checkout, better authority status).
In short, there are simply too many ways that gaming of snippets can be detected IMHO.
What worries me, is that people like us who have had rating data for over a decade but chose not to put it up (until now when we can showcase it through snippets in SERPS). Hope Google doesn't interpret this as spam, specially as we (the small site that we are) have far more ratings than even Amazon for certain products.