Jackson seems, at first, to take the most license with the character of Radagast the Brown.

FORBES: Review: The Hobbit: An Unexpected Journey and The Mooreeffoc Effect

The brief scene between Radagast and the Necromancer was certainly more haunting.

FORBES: 'The Hobbit' Review Part Two: An Unexpected Journey In 3D

In the film, Radagast discovers the Necromancer of Mirkwood (in the tower of Dol Guldur in Mirkwood) and then hastens to warn Gandalf and the rest of the company.

FORBES: Review: The Hobbit: An Unexpected Journey and The Mooreeffoc Effect

Radagast did, in fact, live on the Western edge of Mirkwood, and could easily have encountered the Necromancer in his wanderings through the dark, forested area near the Tower of Gol Guldur.

FORBES: Review: The Hobbit: An Unexpected Journey and The Mooreeffoc Effect

For example, the delightful Sylvester McCoy plays nature-caring wizard Radagast the Brown, who tracks down the source of mysterious illness amongst the fauna of Mirkwood to the supposedly abandoned keep of Dol Guldur.

FORBES: Review: The Hobbit: An Unexpected, But Very Welcome, Journey