On a fresh install of EV... even the vault service account (VSA) doesn't have permissions to search other archives... (i.e. if you are logged into the ev server and you right click a user archive under archives... you won't see the "search archives" item at the top of the context menu unless you go to 'permissions' first and add the VSA and give it at least read permissions.
Maybe you have a policy where everyone has reviewer permissions on everyones calendar? if so then everyone would have access to some portion of everyones archve (i.e. the calendar data.) so... the would show up in the list.
If you can see other peoples archives right off the bat then something else is going on.