Mike Snider claims that, until the 20th century poetry, was not written for small groups. I suppose this is a trick answer?
Poetry was written within small groups: in that sense, for small groups. Jonathan is not wrong, Mike. How about one example. A small group is a small group no matter how popular they may have been. The Della Cruscans not only wrote within a small (tho' bustling and popular) group, they often wrote poems explicitly for one another. Check out Mary Robinson's DC work. Moreover, the DCs wrote poetry considered then (Wordsworth famously in his Preface) and now (by many Romantics students/scholars) to be pretentious, affected, and rhetorically ornate. --Mike, it's the kind of poetry you praise at every opportunity.
Don't look now.