It looks that I missed the debate.
Lazer, there are a number of those cases in each district. Remember, you have to demonstrate continued fear of persecution when GC is approved. USCIS assumes you do when they approved your case, as most of those cases skipped interview. However, if there is evidence, like you went back shortly after GC approval, that contradicts that story, yes they can revoke it. And they did in a few those cases.
Just want to add something to "Thankful"'s 120-day rule: Not every district has the same view - some clearly views that the "examination" does not equal to "interview", which means that you can not sue them even after 120 days after "interview". Yes, most districts feel the opposite way, and the 9th Circuit sided with the N-400 applicant. So, the only thing for sure is that if you live in CA, WA & OR, yes you can sue them 120-days after interview.