And I don't even know if it would work that well. Per-IP edit limits would only stop PR companies with deep pockets for so long. They would do what the russians do, and just make account farms.
 Or so I've been told. I'd love to see actual stats on this. It probably follows a Pareto distribution; but with what power? https://en.wikipedia.org/wiki/Pareto_distribution
I'm sure whitehatwiki.com would have been called exactly that if it were from Russia or China.