Freeze Yer Buns Challenge, you run the problem of having visitors over who might not, say, appreciate the lowered temperatures. When you're acclimated to 70+ degrees it's really hard to drop the 5 or 10 or 15 degrees in one fell swoop.
Generally, when we have visitors over, we are also doing a lot of cooking and, by virtue of having lots of mammals over the house (i.e. human visitors), it tends to heat up naturally. Sometimes, however, the oven and human body heat just isn't enough and we'll turn the heat up for their benefit. If we're all sitting around, blankets can be used, but aren't exactly helpful at a dinner party. And, since we don't have one of those neat, heated Japanese dinner table thingies (aka a "kotatsu"), I don't expect our guests will have a pleasant time eating if their teeth are chattering. So, we turn up the heat.
My mom and brother have learned to dress warmly when they come over and my brother always remembers to bring over his slippers, which I find very entertaining. Not because I'm trying to torture him or anything, but just because he's always so prepared for everything (the OCD helps).
In any case, what do you do for the holidays when you have visitors? Make them tough it out or turn up the heat?