Saudi Prince Al-Waleed Bin Talal is commonly referred to as the richest man in the Middle East. Forbes currently pegs his net worth at $21.2 billion, while Bloomberg's Billionaires Index says it's closer to $32.7 billion.

But who cares about that difference, anyway? What's a few billion to the world's richest?

It turns out that in the case of Prince Al-Waleed, it's a big deal. In 2013, Forbes began pushing Al-Waleed's people for more transparency with regard to the underlying businesses representing his vast fortune. When Al-Waleed was displeased with his overall ranking and Forbes' valuation methods, he filed a libel suit against Forbes in London.

To find out how Prince Al-Waleed accumulated his vast fortune (hint: it isn't family money or oil), and why he's so upset about the Forbes ranking, check out the following slideshow.