Jack is right - it is a huge marketing ploy, with some small basis in fact.
 Personally I find it harder to get kids off of formula (they grow used to
the taste) and don't care for straight cow's milk at a year.  Frequently
become very constipated.  I have parents use 11-12 mo as a transition time
of slowly mixing amount of formula to cow's milk, starting with 2 oz milk
and 6 oz formula, then slowly increasing milk and decreasing formula.
Probably 75 % of our babies are on WIC and at 1 year the formula faucet
dries up, period.  I also have problems with parents who give way too much
milk and juice  and it is hard to explain that toddlers need food not
endless supplies of bottles.  Gets very frustrating.  I love the breastfed
toddlers, they drink just the right amount and learn to eat family foods
because they are used to a variety of flavors (from mom's milk).  {Haha
gotcha -  we don't "know" how MUCH milk they get, but I "know" it is the
RIGHT amount.}   Sincerely, Pat in SNJ