The string 2-group is supposed to play the role of the spin group, but in string theory instead of quantum mechanics. Several aspects of this analogy are by now well understood. In this talk I will talk about joint work with Matthias Ludewig and Peter Kristel on a further aspect, namely the representation theory of the string 2-group. This was an open problem for a long time. Our solution combines higher-categorical topology with operator algebras, and allows a neat definition of Stolz-Teichner's "stringor bundle" as an associated 2-vector bundle.