I've had rattles in my dash, passenger front door, driver's front door, and the right side of the cargo area (near the subwoofer).
I had all of them looked at and fixed by the dealer within the first 12-18 months of ownership. I know a lot of folks here decide not to have the dealer look at the rattles (for fear that they'll make it worse), but my expectation for a new $30K+ vehicle is that it'll be rattle-free.
I recently rode in a Lexus RX (an '07) and was surprised at the number of rattles I heard coming from the empty cargo area. It's possible, though, that the rattle was from the metal license plate frame from the dealer.