With the difficulty I already laid out in mind, it still penalizes people for trying to contribute, but now they get to do it blindfolded.
Presume that a Skill Challenge calls for people to recognize a family crest on a marker or shield. Or perhaps it calls for someone to know the history of a particular battle, or to recognize that a map has been altered. Normally it doesn't hurt to have several people think about the crest and try to recall whether and/or where they've seen it before. Normally it would help to let the party look over the map and familiarize themselves with where they're going. But if it's in a Skill Challenge it becomes crucial that certain PCs don't think, don't even try to notice things.
Presume that a Skill Challenge includes a Spot/Observation check: In a normal situation it wouldn't hurt at all to have several people looking around, but now suddenly it does. Everyone who fails to notice the clue should, by the rules, count as a failure. Those who aren't specifically trained as observers really should be attempting it blindfolded. It improves the odds of a success for the group.
Now explain to me how that's a good rule, how it can be anything other than artificial and contrived?
And if you don't tell them that it's a Skill Challenge then you're adding bad DMing to bad rules, in the hopes that the result will somehow turn out well.
Like I said, I appreciate the value of a game mechanic that lends structure to non-combat encounters, and gives a stable formula for rewarding success, but the 4e implementation is a bad one. Very much a square-peg-in-a-round-hole kind of thing, or at least that's how it looks from where I've been sitting.
I've said many times that a good DM can make any system work, and a bad DM can't make any system work. What we need are good rules for all of the other DMs that fall between the two extremes.
In myopinion, Skill Challenges, as laid out in 4e, don't make the cut.