So as I understand the system, each beneficial circumstance can provide a +1 bonus to a challenge. Such circumstances can include things you describe, or items you're carrying, or other people helping you. That last part is one way you can take part in a group challenge: "I'm going to search this room, Bob and Joe-Bob are helping me search."
There's also challenges that involve multiple targets working independently on the same thing. Maybe five people are trying to shoot the same person, or you've got two or more folk researching a library at the same time for a specific piece of info. Each of those people throw against the same target at the same time.
Unless I'm wrong, you can use either of these methods for the same type of action. The second method is far more preferable than the second one, though, because it has a higher chance of an automatic success (the more times you can throw for an action, the higher you're chances of getting a 5 on the throw).
My question is, would it be a good idea to limit group challenges to one method or the other? It seems to me that characters should have multiple means of achieving something, but players should not.