(hastily starts formulating a reply before swissbob can PM her

)
Really? I quite like it myself (but then I'm a bit of a nosy nellie anyway.)
It's new since a couple days ago, although as mirfield says the same information has always been readily available: just go to "Who's Online" and sort by location.
(In fact, if anything this way is slightly
less stalkerish: the "Who's Online" listing would also tell you how long ago each user started viewing it, and whether or not they're replying.)
Of course if you do start to get any nasty PMs as a result of your sneaking thread-voyeur ways

just let one of the mods know and we'll have a word in the person's ear.