Moth3r said:

Centre channel speakers should be matched to the other speakers, and not be weaker.

You can listen to mono soundtracks through the left and right speakers (effectively creating a "phantom" centre) but this is not ideal - you need to be sat dead centre between the speakers. It's better to use a "real" centre if you have one.

1.0 tracks default to the centre speaker because that is the ideal way to hear them.

This is how I listen to some of the mono tracks I have, but I do know it can sound off on some peoples setups, dialogue in particular. What I still don't get is why do most of the releases including a mono track, include it as a 2.0 mono track when the guide at the Dolby-site states it as an "incorrect" and unnecessary way of encoding a Dolby mono track. Any special reason behind why most companies do this? I think many of the Criterion releases have them as 1.0 though.