Inexpensive umbrella ring flash

I saw a photographer that had a light bouncing into a large umbrella and then he put a cardboard disk in front of it. The light setup was set at the camera's height.

When he took the photos, the results looked like he had shot the session with an expensive ring light. The setup looked like this:

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yep, I've seen this before. Easiest way to make a ring light, that's for sure

What are some examples of situations where you would use this setup? What is the advantage of blocking the light from the center?

These are examples of photos taken with a ring flash (mostly used for glamour) that are from http://www.splatmagazi​ne.com/splatgirls.htm

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In the second and third images (especially #2) the model is surrounded by a shadow on the backdrop. I don't know if that was intentional, but it looks kinda weird to me. I like the effect on the models, though. Perhaps getting more distance between her and the backdrop and lighting the backdrop with a separate light would solve the problem.

To get the real ringflash effect you have to shoot THROUGH the ring.
I have build something with lightbulbs and it has a good effect but it's not the real thing .

The real trick to making this umbrella ringflash set-up work is to use a large umbrella and keep the camera close to the light center.