I did not know this but apparently a pyramid scheme with this structure is called an 8-ball scheme (see 8-ball diagram in http://en.wikipedia.org/wiki/Pyramid_scheme).
It is apparently so common that there is even a pyramid scheme scam calculator online http://homepage.net/pyramidcalculator/.
Btw, to truly know your level number you’ll need to know how long the scheme has been running, but you’ll get some idea of the recruitment required even if you assume it is a fresh pyramid and you are on level 4 (the bottom).
This is a great visual of how it grows, but it needs some context. Still, if you notice that the number needed for each level to split again outstrips the number of women in it, this graphic demonstrates why it does not make sense that this could be sustained when women join multiple circles. http://michaelrienstra.com/8ball/
See another concrete example with numbers in this essay – http://people.ucsc.edu/~rosewood/writing/essays/pyramidgames.htm – it illustrates the unsustainability issue really well.
This newspaper article describes an Oregon pyramid: http://www.mailtribune.com/apps/pbcs.dll/article?AID=/20120120/NEWS/201200324.
Personal experiences on this reddit page – http://www.reddit.com/r/Scams/comments/170f1p/beware_the_pyramid_scheme_women_empowering_women/