Also, my PCs are commonly going around all together to interview people.
In the case of dealing with a reticent, intimidating but socially inclined opponent (such as, say, a Sphinx), should their "targets" be rolling their Social attacks against all the players at once (for example, rolling an Intimidation check against everyone at the beginning and dealing Social stress if the players fail their Defense rolls) or does any attack against a group need to be split like a Spray attack in a gunfight?
I would let them hit the whole group at once, even though that's probably not technically correct by the rules.
That said, I don't think that "interviewing" people should be a constant flood of full-scale social conflicts. If the other party doesn't want something from your PCs as well, it's not much of a conflict and better settled with a single roll.
Whenever you go into a social conflict, you need to have a goal for the opposing part if the PCs lose. Preferably a more exciting goal then, "I want them to go away." If they don't have a goal of their own, it's probably better a single roll than a conflict.
Just thought of this: should the opponent instead be using the Intimidation check as a social maneuver to set an environmental aspect Intimidating which can then be tagged for free in an appropriate later social exchange with whichever player it likes?
By thwe way, you're aware that Intimidation can also be prvocation and mouthing off, right? It doesn't have to be threats.