It kind of makes no difference from the standpoint that a speaker is a speaker. What just-some-guy may be getting at is that some centers are designed for a horizontal placement and it may have issues being stood up on end. Some, like mine, are identical so it is intended to be used as a center or main and I use another pair as surrounds as well.
If you mean can you hook both left and right channels to a single speaker, the answer is no.
