> adopted a policy of technically firing everyone from any startup they acquired, and then re-hiring them immediately under the same terms

Hmm, interesting. I know of a recent case in New York State where one company acquired another, but selectively retained its employees. The acquiring company thought that it was simply not hiring everyone, rather than firing anyone. One of those people sued for unemployment, and the court found that the acquiring company did in fact have to pay unemployment for the employees it "did not hire".