One of the more interesting statements made in Gary Hustwit’s Helvetica:
The classical modernist line on how aware a reader should be of a typeface is that they shouldn’t be aware of it at all. It should be this crystal goblet there to hold and display and organize the information. But I don’t think it’s really quite as simple as that. I think even if they’re not consciously aware of the typeface they’re reading, they’ll still be affected by it, in the same way an actor that’s miscast in a role will affect someone’s experience of a movie or play that they’re watching. They’ll still follow the plot, but be less convinced or affected. I think typography is similar to that. A designer choosing typefaces is essentially a casting director.