I think a cagy and shameless promoter would hold back information to increase anticipation and laugh his ass off at our salivating.
I expect nothing different than people thinking that on a forum dedicated to woo!
My process is pretty simple - I find out someone is confirmed, the people working on the show get notified and then I make the graphic and tweet it out.
Look at last week - I announced our guest late in the week because that is when we had a confirmed guest. Ideally I would love to be able to announce a guest for the next week at the end of a show and have an entire week to get word out.