it seems relatively safe if people do A -> B -> C -> A (A and C are the same person with different emails and bank accounts and credit numbers). However, since A and C use the same SSN, won't it raise an issue that the person could receive >$20000 a year and would be reported to IRS?
Exactly my point. With even two accounts your SSN will have received $24K, which is greater than the $20K trigger point. What do you do then?