It appears that the BATF&E are raiding businesses that sell 80% lowers; Specifically, manufactures of polymer 80% lowers.
Polymer80.The Prince Law office that focuses primarily 2A issues, posted a article titled,
IF ATF COMES A KNOCKING, ONLY SURRENDER YOUR 80% FRAME OR RECEIVER UNDER PROTEST! which is well worth your time to read. I am printing the article and printing up a form 3400.23 just in case the BATF&E agent that shows up at my door does not have one handy.