"Last updated..." on a CV? Should one include a "Last updated on [DATE]" footer at the end of an academic CV? Why or why not? 

(I would imagine that context matters. For example, perhaps it wouldn't be advised for a CV that I would submit as part of a job application, but perhaps it's worth including on the version of my CV that I post on my institutional website.)
I almost always include a last updated date on my CVs. There are numerous online copies of my CV that I am no longer in control of and I think it is useful that people can see that what they are looking at is 10-20 years out of date.