Boldin's wikipedia entry states:
In the offseason 2008, Boldin requested a trade. Cardinals other wide receiver signed a 10 year, $40 million deal. Boldin's had 3 years, $12 million remaining on his contract. As of August 22, 2008, The Dallas Cowboys and the Philadelphia Eagles were looking to acquire Boldin.
The Cardinal's messageboard has a moderator claiming inside knowledge of a deal sending Boldin to the Birds. Click here for the thread.