There was an exhibition a few years ago at the Brooklyn Museum called "Vital Forms," on shapes like this throughout American design in the mid-twentieth-century. Catalog here and archive of the exhibition here.
I am curious to know what Typophiles think of Brendan Stromberger's (bstrom's) post:
[...]Helvetica (or Univers, or whatever) for the logo and branding of a kindergarten[...]
While every designer should be aware of the history (and therefore, the myriad legitimate reasons why things are or aren't done in a certain way) surrounding design issues... to say that one should always use Helvetica over Univers or Arial, what-have-you, is a tad simplistic. They're all lovely typefaces, and each designer will fall into their groove of using a particular one over the other - based on the type of work they do (nature of clients, etc.) and their personal aesthetic.
Nick makes some very good points, however, about the real-world connotations that these highly-similar faces have. I personally find the horizontally-sliced appearance of Helvetica to be rather machined-looking and harsh, as if the letterforms of the 'e' or 'c' might cut you somehow... as a result I use Arial much more frequently. To me it seems friendlier and equally professional.
Some designers use Helvetica exclusively, because it "cannot be improved upon" and therefore should always be used. This is neither true, nor is it worth arguing in much depth. To each his/her own!