People of some religions (notably Islam) have trouble with traditional money and banking services because riba is forbidden.

(http://en.wikipedia.org/wiki/Islamic_banking)

It's the informality that I find interesting. WU is definitely not the same in that regard.

I am not sure it is a big deal, other than that it is relatively unknown here, and the mindset here tends to be that financial transactions need some kind of monolithic centralized authority to be involved.