If /u/6849 is worried about concerted personal vendetta/spying then it would be easy to tie accounts together through looking at the domain... under the assumption that the adversary had access to multiple compromised accounts of theirs to get the addresses used for those accounts in order to tie their domain names together. Unlikely, imo, but it depends on their situation.

I didn't mention above but I actually own 2 domains. One is for services that have my identity anyway (banks, IRS, etc) and another is for services that don't have my identity but I like to use (Netflix, Amazon, etc). If someone obtains a few of my e-mail addresses for the first one, it doesn't matter since they all tie back to my real ID anyway. it's no different than someone using their 1 single Gmail address for everything in their life. If someone gets a few of the e-mail addresses I use with the second domain, they won't be able to figure out if it's 1 person or many other people. They have a similar pattern in formation, but the alias names I associate with them are are all unique.