Good points! I hadn't remembered that there were few/no ships near Earth when Enterprise launched. Where the heck were all those other ships? Anywhoo... you're right in that Starfleet, at least the physical fleet, would be short one ship but otherwise unaffected. Now with the loss of Vulcan in ST09, I think that should slow down advances in technology, since those vast learning centers are gone. Of course, Marcus compensates for this in STID by bringing back Khan and building Vengeance, so YMMV.