Yeah, it's hard not to do that when the goal is one person one income. There's another project that's planning on using iris scans but how the hell are people in Africa going to get their irises scanned. I don't even know how I would do it here in USA. You have to build a whole infrastructure. So using cell phone numbers as a proxy for personhood isn't perfect but it's good enough to try the concept out.

Edit: damn bilingual autocorrect