On my Droid I had a screen protector on it basically its entire life. I ended up taking it off about a month ago and noticed that the screen still held up well and I didn't have one single scratch with the protector off.
With my fascinate, I decided to pass on the screen protector because I was confident I wouldn't get scratches. I'm VERY careful with my phones (more than most people), so I was very confident I wouldn't get any scratches, but today I noticed I have two very tiny fine scratches.
Wish I would have just went for a screen protector in the beginning now. Oh well, I just ordered realook screen protectors off ebay so I'll just have to now protect it from further scratches.