Tornadoflame
Super Freak
Actually one flashback scene of pre-rebellion events was allready filmed.
It was the scene of.Ned Stark's father and older brother being cruelly killed by the Mad King before the eyes of the whole court.
You can see a glimpse of that scene in one of the promotional trailers for season 1.
Unfortunately the whole idea of flashbacks was scrapped due to time and production restraints. Which is a pity couse it was the perfect storytelling tool for the creators. The TV show misses a LOT of context for events and characters due to the lack of any explanation of passed history of Westeros. GOT is a great show, but the constant productional restrains keep it from utilising the whole potential of the novels and make it seem crude in narration compared to other HBO masterpieces.
Yeah, it takes away from the feel of the story being told. This story is so deep and not showing or delving into the past prevents people who don't read from getting a full understanding of the characters and the families. They think Vicerys is just upset for no reason and that Robert is just a fat, drunk, slob. Some people think what happened to Catelyn was completely undeserved, but truthfully she was just as spiteful as anyone else. I love this story.