Dear Colleagues:This letter is about our news embargo: what it is, why we defend it so staunchly and why we think you should, too.Many of you subscribe to the Journal. Those who have it delivered in the standard way by second-class mail usually receive it on Thursdays, as do most of our other regular subscribers. Depending on the vagaries of the mail service, your copies occasionally arrive a day early and sometimes one or two days late. Some of you, including the national wire services, the major networks and some newspapers and news magazines, pay for first-class . . .