The Twitter watch-out memo. How many of these things have we seen? You know, the admonishments from management that reporters are representing their media outlet every time they take to Twitter and Facebook and the like. The ones that stress decorum and sanity and non-offensiveness.

Deadspin today dredges up another exemplar. It’s from ESPN, and it carries pretty much the same authoritative and preemptively scolding tone as its ancestors. Here’s the money passage:

In short, it’s in everyone’s best interest to be smart about how to participate in social media circles. Twitter is truly another stream of media and, when used wisely, is a wonderful tool for you personally and for our company. That said, it is not your personal playground. It is not a place to incite arguments, render threats, divulge company information or opine endlessly.

A theory from Deadspin on the provenance of this memo: “It’s suggested that this memo was in response to Ric Bucher’s ill-advised ‘sweet and sour’ reference to J.R. Smith, recently returned from China.”

ESPN takes issue with that archaeological supposition. Says spokesman Josh Krulewitz:

“We’ve had existing social media guidelines that we are often updating. As part of that, we look for opportunities to regularly communicate and provide guidance, especially given how quickly things change in this media environment. This particular update had been in the works for a while.”

ESPN has about 1,000 commentators whose extracurricular utterances could somehow embarrass — or, indeed, ennoble — the sports behemoth. So it makes sense that it would send out finger-wagging reminders to its people.

Not that these efforts at control ever seem to work. The notion of guidelines and rules are alien to Twitter, which is all about churning out fun and daring thoughts that very nearly cross the taste line. In pursuing that ideal, famous tweeps often step over it. As the New York Times’ David Carr wrote, “contemplativeness is not generally a Twitter impulse.”

Which is to say that memos from management on Twitter policies will continue to issue from news organizations; they’ll continue to get excerpted in media blogs; and they’ll continue to have no impact on Twitter.