Or, yet another iteration given that the rules of engagement (the TOS) are the vaguest set of rules regulating a multi-billion dollar industry you've ever seen:
Rules? What rules. Google doesn't have to give you rules, tell you how to rank or what gets penalized.
And few if any get penalized by bending the 'rules' of Google's guidelines one time. Normally it's the result of stepping way over the known guidelines, repeatedly and sustained. It should hardly be a shock.
And sometimes, you'll get demoted just because they did an algo shift and you don't fit the new calculations. No rules, and they don't have to tell you this.
As noted, the point here - and it's a good one, is that Bing can produce some level of conversions. I don't touch bing myself but I know in my industry it produces some of the best sales there is.