I know I'm late but...
This is an interesting topic for several reasons. I am always surprised when ppl don't know which celebrities wear lace fronts b/c so many of them do. My personal opinion is that Oprah's hair is a lace front. This is partly b/c I've been told this by several hair stylists but mostly b/c it looks like one.
I think some ppl are just more familar with weaves and lace fronts and thats why we can spot them. I know a little about lace fronts b/c I was going to get one at one point. I did quite a bit of research and spoke to some hair stylists about it.
FYI, if you have a lace front and somebody runs their fingers through it, they will feel nothing. Tracks only occur with a weave- and FYI I've had weaves done where you couldn't feel the tracks. Lace fronts are virtually indetectable when done right if the hair is good quality. It is glued to the skin around your forehead, nape, behind your ears etc. Your natural hair is usually braided underneath but the way in which the wig is put on, you won't be able to feel the braids (if done correctly). With a good lace front, you can wear ponytails and even corn rows. Its extremely versatile.
I think its possible that Oprah has long hair but the hair she wears on TV doesn't look like it grew from her head. Esp the ringlets. It just screams lace front to me. I am fully aware that black women can grow long hair as I'm one of them. I'm also not "mad" that Oprah wears a wig. But I call a spade a spade. Maybe that's her hair in the pic/video with the orange headband but the headband is an odd touch if she wanted to "prove" her hair is real. People often wear headbands to cover the line where the weave hair and their own hair meet when wearing a sew in.
I think some people get annoyed when people bring up these topics with a suspicious tone is b/c they don't understand where they're coming from. Granted, some ppl take it too far and care way too much about other people's business but a lot of times, people are just curious.
Moreover, there's a real emotional component to it. People get tired of celebrities having seemingly perfect physical qualities and have a need to prove this wrong. How else did the Beyonce pic with glue on her face end up floating around the net? Or the one where she has an inch of hair in a ponytail? It *does* bother people.
But its also just an interesting topic of conversation. I don't think anyone's saying anything bad about Oprah so it is what it is. That's my 2 cents!