Of course it was planned, but you have to wonder why...
(Or a few quick thoughts on Janet Jackson's lady bumps).
From the various high res shots making their way round the 'Net, a few things seem fairly clear:
1. Her rather strange Hellraiser costume was clearly designed with removable busten-halter bits: those weren't just studs around the boob line, they were snaps.
2. Why would anyone wear such an uncomfortable looking nipple ring under tight-fitting latex unless they intended to show it off later?
3. Justin clearly knew exactly what he was doing - knew the snaps were there, and knew exactly where to pull.
4. So the only question that remains is why, Janet, why did you choose such a dreadfully unflattering outfit?