From the Comic-Con Teaser-Trailer:
. The USA government wants to aprehend Tony Stark's technology because it is a "privatized weapon". Stark doesn't plan to give up on his technology knowing they'll use it as a weapon, and becomes an public enemy.
. The government, aided by weapons manufacturer Justin Hammer, develop the War Machine armor to fight Stark/aprehend his armor. Col. James Rhodes, struggling between his friendship with Tony and his loyalty to America, is designated to use it.
. Whiplash has a personal rivalry with Stark's family, calling them "Butchers and murderers" who inadvertly destroyed millions of life. And, when Stark's blood fall on the water, the sharks will come.
. Black Widow is infiltrated in Stark Industries.
. Stark doesn't want to participate Nick Fury's "super-secret boy-band".
. Stark likes Donuts.