Star billing is weird. There are movies where actors are billing before the title but on the poster their name isn't one of the big above-the-title names (Gary Sinise in Snake Eyes, Gene Hackman in The Firm, Gary Oldman in Air Force One, Alec Baldwin in Mercury Rising, Charlize Theron in Hancock).
Supposedly, Vin Diesel didn't return for 2 Fast 2 Furious because he wanted sole title billing.
I understand Will Smith being the main selling point, since he is currently the No. 1 box office draw, but I don't understand leaving Charlize Theron out of the marketing.