I think it has a great deal to do with the size car you have. We have a 4wd so its easy to have a bub in the middle. DD was put in the middle because we to were told that was the safest place. She is now on the passenger's side and DS is in the middle.

I dont think car manufacturers allow for enough room in the back of sedans for car seats. Its sad because there are some nice cars out there but i wont go back to one because of the room issue.