One reason to filibuster the Estrada nomination, quite beside the fact that it might work, is that it allows us to see which Democrats in the Senate are worth keeping. One member still on the fence, Mary Landrieu, is quoted here as saying that while she is impressed with his personal story, she has some doubts that he is in the "mainstream". If he is having problems getting the support of one of the most conservative Democrats in the Senate, someone who boasted in her recent campaign for reelection how often she votes with the President, it signifies that his nomination may be in trouble. Keep up the pressure, kids.