There are 506m mobile subscriptions in Africa

"The number of active mobile subscriptions in Africa crossed the half-a-billion mark in the third quarter of this year, to reach 506 million at end-September, according to research by UK-based Informa Telecoms & Media.
The report, published on the researcher’s website said at the end of the third quarter of this year, Africa accounted for 10% of the world’s mobile subscriptions and was one of the world’s fastest-growing regions – with the subscription numbers increasing 18% over the year to September."
Source:  Data from Informa Telecoms & Media, reported by PeaceFM Online, 14th November 2010
[Note - the story is not easily accessible on the Informa website]