I keep on reading that cosmologists contemplate two possibilities: either the universe is closed, unbounded and therefore finite, or else it is open (possibly flat) and infinite. I hear that a flat, finite universe "introduces many problems" and is discarded. My question would be "what problems?". I understand the the observable universe is smaller than the whole thing, so I cannot see a problem with this notion. In such a universe, there would be some observers who would certainly see anysotropy, but that would not be the case for the majority of the observers, would it? What other problems exist?