I've been told I "collect" cute underwear. I have a LOT. I wear them all, but you won't find a pair of plain panties in my drawer. I do have one white pair of boyshorts with buttons and bows on em, but I reserve those for special occasions
As for what type, I am a thong girl unless it's that time of the month. I can't stand the bunching from bikinis or anything else for that matter. I'll go commando if I'm wearing a skirt or something that isn't really tight. I could NEVER rewear a pair of jeans after going commando, and I always try to make one pair of jeans last for at least 2 days.
Now for the whole wearing underwear to bed thing.... I have NEVER had problems with my nether-region and I wear underwear to bed every night unless I'm home alone (which isn't often). The only times I've ever had a yeast infection was after a round of antibiotics. So, I think that theory is a load of hooey unless you're wearing like silk or satin undies to bed every night.
I'll put my $.02 in on the yogurt thing, too. As an IBD patient, I know firsthand that live cultures (or Probiotics) are good for the digestive system (and can be somewhat beneficial for your nana). Now if you have a disorder in the GI tract like I do, you'd have to eat a helluva lot of yogurt to get any real effect. That's why they sell just the Probiotics in healthfood stores. Okie doke, I'm finished now...