Spraticus:
the whole thing is a category error. Saying that Marina Abramovich just being in the building is a work of art is the same as saying that bread is a form of sausage or a flower is a pair of scissors.
I guess I would disagree with this. I think Marina Abramovich becomes art the moment you perceive her as such. The standard for determining what art is entirely depends on how it is taken, and if it is taken AS art, it is. Not unlike saying, in the building, my doesn't Marina look lovely. You could also have said, my what grace, or, what nerve she has coming here, and so on. Each occasion, brings a new interpretative standard.
As to an error in category, I would say if you're dealing with fitting flowers into the category of sausage, it does not work our well usually. You could imagine fashioning a flower into the shape of scissors, then drying them, petrifying them...but forget it. Can't meaningfully be done. But Marina Abramovich fits nicely into the category of art, as do, frankly, all things: anything can be
taken as art.
Sausage can be taken as art, but not everything can be taken as sausage.
Anyway, categories are fluid things, and one often can be taken as something beyond the usual. A loaf of bread can easily be taken as a door stop or a plaything for a dog. Categorical errors occur only when the one excludes the other for the particular occasion at hand, or simply altogether.