I posted a link to Candor[1] last week. Wharton's Adam Grant makes the compelling argument that "group ideation" tends to produce less innovative results. Creativity and shyness tend to be correlated after all. And consensus around a "winner" often forms prematurely due to "anchoring" and "clustering" biases.
By decoupling the two regimes, and perhaps even anonymizing the idea from its creator, you've got a winning chance of allowing team members to unleash their inner Jungian Shadow, and give reign to the daemons of inspiration ;)