at this point, i am imagining that the phone must've been having some obvious functionality issues that had to be fixed. they are working to ensure it's not a problem before they ok the launch. market pressure (competition, public opinion) has reached a point that they would release the phone if it were essentially working well - even if certain functions weren't perfect, such as skype mobile.
vzw's previous hints at an ahead-of-schedule release date allude to the possibility that they initially thought the phone was ready and were responding to market pressure. clearly, that is not the case. reports tend to say that verizon is merely making sure their first 4g phone is perfect, but i think it's more like they want to make sure they don't go into battle with an unloaded weapon.
probably another worthless theory.