The AAP just came out with new guidelines suggesting what car-seat safety folks have known for a long time - kids should be rear facing in the car for as long as they are within the limits of their rearfacing convertible carseats - not turning forward facing until they are at LEAST 2 years old.
Those who ride in my car may know that Lexi is still rearfacing. She is 2years, 10 months old, and weighs 35lbs. Her seat will keep her rear facing until she weighs 40 lbs. The way she's been growing this past year (SLOWLY) she may make it to 4! (Or not, if she has a growth spurt.)
Ideally, kids would stay RF until they are 4-6 years old. That's when the spine finishes hardening and the neck becomes more capable of handling a whiplash situation. Realistically, there are MANY seats out there that will keep kids rear-facing until they weigh 35 or 40 lbs (and one that goes to 45 lbs).
Here's what everyone looks like in our car! Lexi was not in there (she was too busy on her swing) so we just have the two boys to demonstrate. Three carseats, all rearfacing in the middle row of our van (a 2007 Honda Odyssey. Hey, there's room for three more kids in there! I'll get a pic of Lexi rear facing soon. Yes, her legs are bent, but she finds places to put them and has always been very comfortable. Trust me, this kid will complain if she's not comfortable!