The Garden of Endangered Metaphors
With a certain anguish of soul, I note that "free reign" seems now to be the accepted reanalysis of "free rein" even among quite educated people. It makes some sense, of course, and as a figure of thought it makes more sense to the average person of the 21st century than an equestrian metaphor.
Metaphor and the fallacy of conversion
Joshua Landy just posted a very interesting blog entry here, partly on how the fallacy of conversion tends to work in Derridean argument.  I am no longer enchanted by Derrida -- I've been... deconverted? deprogrammed? -- but I was prompted to defend him in the comments to that post.