Are soap films ideal 2D fluids?

Soap films are very thin, but their thickness is finite. To what extent can they be thought of as an ideal two-dimensional fluid, and to what extent does the three-dimensional world intrude? By following the Brownian motion of tracer particles embedded in the soap film, my lab learns about the flow field of the film. Our experiments show that the soap flow fields are indeed two-dimensional in character, but that they are never ideal. Furthermore, soap films that are ``too thick'' are even less ideal.