Last year, at my dad and step-mom's house, they had 6! There were 3 designer trees in pots (maybe as tall as me, I'm 5'7", from the bottom of the pot on the floor to the tip of the tree) in the living room, the dining room, and the family room. One was a tiny ceramic tree in the kitchen, there was a fiber optic table-top one in the entry-way, and then the HUGE tree in the basement - though no one could be bothered to decorate it! (When I still lived at home, the year before, there was 7 because I put up my 4 foot tree in my bedroom as well.)

At my apartment, we just had one, my four-footer. This year though, we are getting a six foot tree, I'm really excited. I don't think we'll have more than one at our place though, because we live in a one bedroom apartment and we just don't have the space. Unless we put one out on the balcony... Hmm... lol