Is it necessary to see yourself whilst you vlog?

Most youtubers have a camera where you can rotate the lcd screen. Is that necessary. Can you use a camera that doesn't have that feature. I have a nikon d3100 and id like to use that to start vlogging, please help?

No, it's not always necessary. It's just to make sure you know where you are filming because if you do all this vlogging and then it turns out you're not in the frame, it just ruins everything.
If I'm ever in a situation like that I ask someone if I'm in frame or if you stand in front of a mirror while holding the camera you can see the screen so if you need to move positions to get yourself in frame.
~Hope that make sense/helps!