Unfortunately I made that mistake with my original SSA 3DS portal as you can see:
![[User Posted Image]](http://www.darkspyro.net/images/portal_leak.jpg)
Luckily after cleaning it up the portal still worked but if it had been left longer I would imagine it might not have fared too well.
And even if you've just left the batteries in the box they can still leak, a while back I noticed a set of never used batteries in my drawer that I'd left in their original plastic wrapping had started leaking. So anyone who's kept any game with a battery powered portal in its original packaging might want to check inside for damage.