One of the topics I end up teaching students is how to draft a demand letter. I cover the basics: (1) make a demand; (2) make the demand for a date certain; (3) use the persuasive voice; and (4) document the legal and factual basis for your claim.
While I emphasize that the purpose of a demand letter is to prompt resolution of the matter prior to litigation, I do not generally discuss in depth the distinction between persuasive voice and extortion. It’s never really been an issue.
But now I can point to a counterexample of a demand letter gone wrong. Apparently, a judge considered this demand letter to rise to the level of extortion: https://plus.google.com/109385971027097330016/about?hl=en
Whether the implicit threat of revealing salacious details rises to the level of extortion is a tough call, but also an issue that could have been avoided altogether through a more professional, law-focused approach. (“Law-focused” = focused on your legal claims and the relevant facts that support them–not overblown rhetoric and lurid details. I mean . . . “see enclosed photo”?–really?)
Remember people: You’re a lawyer–not an agent, not a bully, and not a politician. A lawyer. Act like one!