My recollection is that "last seen" information was prominently displayed on a user's profile page right after "member since" on the top line.
As I look at profiles today, it is not there.
I have been able to find it in "network profile" page, "accounts" tab. The "accounts" tab appears to be the default display when selecting "view network profile" under "communities". However, some users do not have a "view network profile" link under "communities" - for them, I have to go to "network profile", which opens to a default display of "top" tab and then select the "accounts" tab. This makes it rather more laborious to get to "last seen", which used to be one click away.
I have recently hit 15K rep which has changed some of my displays, but I think this is unrelated.
Can someone confirm that this change was made recently? Was a purpose stated for the change?