I'll have to give a look - mayhaps some forums have it set to turn on, may even over-ride a person's preferred setting (but only in that forum). I'll also check on availability for non-staff per tambo's comment (it may be available to crew as well, in fact I'm pretty sure it is...just not members, since it would be used for testing things out and getting feedback before subjecting the public to it).
But yeah, I'll check into it. Any further comments people can offer would be helpful - what usergroup they are in is something I can probably figure out, but if it happens in certain forums or pages and not others, or if it starts somewhere and then follows you around (and does it change your 'preference' in your UserCP->Edit Options-> last choice on setting preferred skin)?