Okay, so maybe I was wrong about that planted question not being part of a systematic effort by the Clinton campaign. The Grinnell student involved has given CNN some interesting backstory:

Gallo-Chasanoff, an undecided voter, said what happened was really pretty simple: she says a senior Clinton staffer asked if she'd like to ask the senator a question after an energy speech she gave in Newton, Iowa, on November 6.
"I sort of thought about it, and I said 'Yeah, can I ask how her energy plan compares to the other candidates' energy plans?'" Gallo-Chasanoff said.
"'I don't think that’s a good idea," the staffer said, according to Gallo-Chasanoff, "because I don’t know how familiar she is with their plans."
He then opened a binder to a page that, according to Gallo-Chasanoff, had about eight questions on it.
"The top one was planned specifically for a college student," she added. " It said 'college student' in brackets and then the question."
Topping that sheet of paper was the following: "As a young person, I'm worried about the long-term effects of global warming. How does your plan combat climate change?"...
Clinton campaign spokesman Mo Eliethee has said in a statement responding to the initial college newspaper article that the senator "did not know which questioners she was calling on during the event."
Gallo-Chasanoff wasn't so sure.
"I don’t know whether Hillary knew what my question was going to be, but it seemed like she knew to call on me because there were so many people, and…I was the only college student in that area," she said.
In their statement, the campaign also added, "On this occasion a member of our staff did discuss a possible question about Senator Clinton's energy plan at a forum…This is not standard policy and will not be repeated again.”
Gallo-Chasanoff may have some doubts about that one, as well
"After the event," she said, "I heard another man…talking about the question he asked, and he said that the campaign had asked him to ask that question."

Also, Roger Simon has an interesting take on the episode, including this exchange with ghost-of-campaigns-past Roger Ailes:

 In 1988, Roger Ailes, who was George H.W. Bush’s media guru, gave an interview to Advertising Age magazine and was asked if there was a difference between selling a candidate to the American people and selling a box of cookies to the American people. 
“There’s an enormous difference between cookies and candidates,” Ailes said. “Cookies don’t get off the shelf and hold news conferences or make gaffes or go on ‘Meet the Press.’” So the name of the game for presidential campaigning is to control the candidate so he gets “off the shelf” as rarely as possible.
And for those rare off-the-shelf moments--debates, interviews, questions from voters--you make sure the candidate is briefed and rehearsed.

As noted last week, Ailes knows whereof he speaks: He was one of the image gurus who helped sell the box of cookies that was Richard Nixon in 1968.

--Noam Scheiber