One of the metaphors that I think is most damaging is inherent in the way most decision-makers think of programming languages-- the decision is treated as comparable to the selection process for natural languages, which is trivial and obvious for natural languages but very complicated for PL.

With natural languages (a) there aren't order of magnitude differences in power or quality, and (b) the switching costs associated with becoming fluent in a new one are very high, so businesses usually default (without conscious choice) to "the standard", which is the language most familiar to the people in that location. (In New York, that's English; in Tokyo, it's Japanese.) For natural languages, this is the obvious right decision.

When this metaphor is taken literally and applied to PL selection, it results in Java and C++ being used, because those languages are "the standard". The difference is that, (a) there are languages that are orders of magnitude better-- just compare Scala against Java-- than mainstream PL, and (b) switching costs are a lot more moderate. Using "the standard" in PL, for a new company, is a horrible decision; you won't even get off the ground if you start in Java or C++.

Oddly enough, the term "programming language" is, technically speaking, completely correct (a PL is a language) but metaphorically detrimental.