I HATE cliques pretty much anywhere, though I confess I hypocritically wouldn't feel that way if I were part of one. Though I'd like to think I'd at least try to be inclusive of new people if I were in one. I have never been able to deal w/them, not in school, not in grad school, not outside school and definitely not at work (though I have very little job experience). This isn't the same, but grad school does resemble a workplace in some ways and I've never fit into one and I've been in two grad programs. What sucked was trying to make friends w/people you knew you had something in common with, but most of the time they'd be either busy w/their work or research or off w/the clique at department events or even outside in their free time. It's definitely harder to deal w/cliques when you're on the spectrum or, as in my case, there's a significant age difference w/your classmates/cohorts. I'm guessing this is often less of an issue in a normal workplace (the age difference), but it may still come up in regard to some issues.
It also depends on the workplace I'd think. At least sometimes, if you're in an educational or nonprofit environment, that might be less cliquey than at a company, especially a larger one. Good luck dealing w/cliquedom, Summer!