According to the email sent out to subscribers today, Netflix said it would be increasing the Blu-ray rental fee to as much as $9 on top of your normal subscription price.
Netflix's "so called" reasoning is that the available selection of Blu-ray titles has increased and Blu-ray is more expensive for them to stock (I guess they decided to pass that extra expense onto its customers).
The availability of Blu-ray movies was a nice perk for subscribers who already have Blu-ray players, but it is apparently not enough to draw in new customers.