It has been noted both in these forums and other places that the screen was designed to be conductive, and that a screen protector would in fact create problems due to the capacitive touch that the phone uses. I believe that the 'official' Moto forums was one of the places that were referred to in other threads, where a Moto official was quoted as saying that the screen did not warrant a protector.
However, it has also been noted that the screen is not 100% scratch proof - at least one person noted that having gritty material in their pocket has led to a scratched screen, and my personal experience with the cheap VZW protector (the non privacy one, the one that does to cover the 'buttons' at the bottom) showed me that the capacitive touch worked perfectly fine with the protector in place.
I have now been using it without a protector for about a solid week+, and I have found that, while the screen sensitivity is a bit better without a protector than with, knowing that there are going to be times when the phone is in my pocket or in another area where the grit could easily get on the surface makes me worry. By a bit better I actually mean that with the protector in place it was very nearly perfect, and without it seems a bit overly sensitive.
I'd rather have the protector than not, you know what I mean?