I say that it's tacky to ask a question like that. Asking if specific people (for example, a mutual friend) is less tacky.
If I were throwing a party, and a work friend asked if other work friends were going, then I wouldn't think that was tacky (because they're asking about a group of people that directly relates to them). If I were throwing a party, and a work friend commented that it was an eclectic bunch, and am I inviting my grad school friends, I would look at them like they were crazy.
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