Jumping in late here but I think the difference between the Natalie Portman situation and the Jennifer Hudson situation is that Jennifer Hudson should have given them notice. That Natalie is pregnant and could go into birth at any time was no surprise to anyone. Maybe it's inappropriate in industry practice to book a gig in Texas the night before a gig in Chicago, maybe it's just fine, I don't know. I can think of how it would be inappropriate for a lot of other professions - I can't imagine if I were in court on Tuesday, took a quick flight Tuesday night without telling anyone, and then showed up late to court on Wednesday. Actually I can imagine - I'd be fired.
But to me the real issue is the lack of notice. JH is a native Chicagoan, and that week of blizzards was insane. A prior poster said it snows in Chicago, but not everyday. Well, yes, but we do have weather that interferes with travel pretty darn close to everyday in the winter, particularly in the Dec - Feb stretch. I think it's extremely irresponsible to travel in or out of Chicago in the winter for business and not allow for the very likely possibility that your flight will at least be delayed. So given that, and given that JH is from here, I think the least she could have done is mentioned to at least one staffer - Hey, I'm going out of town tonight. The weather reports are good so it shouldn't be a problem but I just thought I'd put you on notice. I realize that her flight was actually affected by surprising Texas weather, not routine Chicago weather, but my thought is that the Chicago weather is what makes it unreasonable for her to plan this trip without even giving anyone a heads up.
As far as Oprah's actions - I don't blame her for being upset at all. However, I do think the "chastising" is a bit much, particularly on camera.