[kbenson]

Sure, but I find most interesting science fiction takes liberty at least somewhere. I'm willing to let the author play a little loosely with a few things, which are hopefully explained as "additional input we don't quite understand alter known theories" instead of "ignore this well accepted thing", if it adds significantly to the story.

FTL communication? Eh, there's both enough new stuff to discover in physics and it provides such a massive boost to most stories that I'm generally willing to allow it, if treated well.

The clone personalities diverging almost immediately? Kinda torn. On the one hand, I think they would diverge significantly eventually anyway (take anyone at age 40 and give them a couple hundred years of experience being a martial protector, trying to unite nations, an R&D head, or a explorer of the wondrous, and you're bound to come out the other side with large differences), so I'm not sure how important it was to have it immediately if the plot points it helped could have been achieved in some other manner.

[arethuza]

I rather like the explanation for the lack of FTL travel/communication around here in Vernor Vinge's Zones of Thought books (first two are some of the best SF novels ever written, third one is pretty awful).

Edit: Added "around here" - which is quite important.... ;-)