I expect this news played a major role in Alias Publishing pulling the plug on Penny and Aggie #4. My sympathies go out to anyone else on the edge of the sales bubble which Diamond is now deflating.
That said, I have been amazed for years at how lax Diamond's sales standards have been, and with these new restrictions in place... I'm still amazed. 500 copies? When I was self-publishing the lower limit was 1000!
I sort of wish Diamond would get out of the business of selling tiny books, because then smaller distributors might actually have a purpose for existing, other than the purpose of... being small and being distributors that aren't Diamond. Keeping Diamond out of anti-monopoly court, I guess.