I have an issue with "Facebook could also choose to insist that throwaway email addresses (e.g. Hotmail, Gmail, Yahoo, etc.) cannot be used for these sorts of c

I have an issue with "Facebook could also choose to insist that throwaway email addresses (e.g. Hotmail, Gmail, Yahoo, etc.) cannot be used for these sorts of complaints - that a domain name associated with the brand which claims to being breached is used instead". Why is it only about corporations? Other people's copyright cannot be violated - say a successful blog that someone hosts on Blogger/Wordpress? Those wouldn't have own-branded email names. Also, it is confusing "copyright" and "trademark" issues (with the mentioning "brands" like that) - the latter is not subject to DMCA, now is it?