This is wrong. My wife and i could fit three carseats ALL rear facing in our Toyota Corolla... it just wasn't comfortable for us. Since we got our Sonata, we can sit all three in the back rear facing with plenty of room for us. You can also do this in the Malibu, Camry, Fusion, and Accord. The secret is finding the right car seat.
http://www.skjp.com/products/97556/Car_Seats
At this site you can find the safest, and at the same time, narrowest car seat on the market. They're pricey, but would you rather spend thousands more on a minivan or hundreds for new car seats?
Oh, and by the way, those car seats will last your kids their entire carseat/booster lives. This, and all of the leading research now suggests that your children should remain rear facing as long as possible.. up to 40 pounds. The vast majority of car accidents are on the front end and a young child's spinal chord is still very fragile. I've done far too much research on this stuff now that I have kids...