We manage a lot of partner / customer user accounts and would like to know when users become inactive so we can disable them. The simplest way for us to achieve this would be if you to include a Last Active date in the portal users section (similar to the regular Aha user accounts).
I agree this would be helpful for security and customer engagement. We don't have the data to deactivate unused accounts, leaving far more open accounts than needed. Last login is an indicator of engagement that can inform our efforts to seek targeted greater customer engagement.