This would be helpful mainly to curators and staff, and maybe to the performance of the site as it grows.
Accounts meeting the “never active” category would have:
0 observations AND
0 identifications AND
0 comments AND
0 other created content such as projects, places, journal posts, etc.,
(EXCEPTION: created user-profile content like descriptions), AND
0 logins for at least 2 years.
In the process of flagging spam accounts I run across tons of these, both “legitimate” and spam. This would have the effect of automatically removing a lot of the older spam backlog, plus “legitimate” but clearly empty and abandoned accounts.
I suggest that such accounts be deleted automatically with no notification to the account, since that could end up sending emails to lots of spammers. Owners of other abandoned accounts who come back after 2 years would just have to create a new account again.
2 years is my suggestion, but better suggestions welcome!