Also because the major browsers have stepped up their rate of innovation. So they now either have: a) Shorter release cycles and test phases b) More changes m

Also because the major browsers have stepped up their rate of innovation. So they now either have: a) Shorter release cycles and test phases b) More changes made in a release cycle without a corresponding increase in the number of testers. It reminds me of the Internet Explorer / Netscape wars (around the time of Netscape 4).