Embattled NBC News anchor Brian Williams has ditched his planned appearance on The Late Show with David Letterman this Thursday. Of course, a 2013 visit on the Late Show is part of what's putting Williams and NBC News in a very difficult situation.

Williams is currently on a self-imposed hiatus after questions have arisen about his claims about his involvement in certain news events. The main incident is how, while reporting in Iraq in 2003, he said that an Army helicopter ahead of his was shot down—but Williams has told the anecdote in more recent years by putting himself in the fallen chopper:

The NY Times' David Carr noted, "Mr. Williams has been on almost every talk show you can think of and that requires not only a different skill set — he is a gifted and funny performer — but stories in abundance."

For some time now, there have been two versions of Brian Williams. One is an Emmy-winning, sober, talented anchor on the “NBC Nightly News” and the other is a funny, urbane celebrity who hosts “Saturday Night Live,” slow-jams the news with Jimmy Fallon and crushes it in every speech and public appearance he makes.

Each of those personas benefited the other, and his fame and appeal grew accordingly, past the anchor chair he occupied every weeknight and into a realm of celebrity that reaches all demographics and platforms. Even young people who wouldn’t be caught dead watching the evening news know who Mr. Williams is.

Which is good until it isn’t.

Carr adds, "I don’t think he should [lose his job] — his transgressions were not a fundamental part of his primary responsibilities." The New Yorker's Ken Auleta doesn't think Williams will get fired either, "[A]nyone capable of a long view knows there are often second—and third—acts in American public life. However, there are some scenarios in which he does not survive as an NBC anchor. One: if more fabrications surface from the work of hundreds, probably thousands, of amateur detectives online—eager to prove that Williams was not telling the truth when he claimed, for instance, that he saw a body floating beneath his hotel window in the aftermath of Hurricane Katrina."

Williams' predecessor, Tom Brokaw, according to a Page Six source, "wants Williams’ head on a platter. He is making a lot of noise at NBC that a lesser journalist or producer would have been immediately fired or suspended for a false report." Publicly, Brokaw isn't taking a stance, saying that any decision "is up to Brian and NBC News executives." Brokaw told Politico, "There is a process underway, and I didn't want to impose myself on to it. This is a very serious issue that must be resolved on the facts. All this endless speculation is unfair to all involved."