In the era of the rookie salary cap, signing a QB who is not under a rookie contract (ie Fitz, Flacco, Romo and probably Dalton ) who is not a certified star will nearly cripple a team unless it is structured in some very clever way. If you don't have a star QB, a team is probably better off rotating mediocre QBs every 4 years on a rookie contract. QB's like Fitz and Jake Locker and Matt Shaub and EJ Manuel and Chrisitan Ponder are all interchangeable, not good enough to carry a team, so you might as well go with the cheapest and spend the money elsewhere.