I can get on board with the idea that it is good to drop the bottom 10% of the company on a regular basis. But they're essentially taking very small sample sizes (individual teams), and assuming their distribution matches that of the entire company.
Or to put it another way, let's say you ranked every employee in the company 1-40,000 or whatever. You are trying to drop employees 36,001-40,000. An absolutely awful way to make that happen would be to create 4000 small groups of 10 people and then drop the bottom person from each group. Anybody who's even somewhat proficient in stats can tell you that this setup will yield results WAY off the mark. You could even quantify it with some simple analysis, and though I don't have time to do so, I'm sure the results would be horrifying.
And that's assuming a totally random distribution of people, which isn't true, and totally ignoring psychological effects of such a system. But at the very least, stack ranking is just bad science, and that should matter to these companies.