Contrary to the the above answer, in the text the word "hipsters" semantically denotes the phenomenon of hipsters, as suggested by the originator of this string. Grammatically it is, of course, a plural. English allows words to take a verb corresponding to the semantic number rather than the grammatical number. This is especially the case with collective nouns such as "faculty" or "company". Indeed, in some cases to use the "correct" grammatical number would sound stilted. "The staff is waiting to meet you" sounds distinctly alien to the English ear. "The staff are waiting to meet you" is the normal English. In the days before the advent of pedantic English teachers it was evidently quite normal for a grammatically plural word to take a singular verb. Thus "small pocks" (or "small pox" in an older spelling) was used in the singular to refer to a disease, so commonly that we now scarcely recognise it as originally a plural. Note, by the way, that I write "small pocks....was", not "small pocks....were". Semantically, the phrase "small pocks" in my sentence denotes the term, not the pocks themselves. Thus, in accordance with normal English practice, I use the singular construction, as the writer of the notice on the blackboard did.
