About a billion people in the developing world have basic smartphones, and for many of them, it's their only computer and communication device.
Now some start-ups are emerging to exploit the opportunities and manage the problems that this creates.
Tala, for example, culls data from cellphones to gauge a person's ability and willingness to repay loans. To its founder and chief executive, Shivani Siroya, the cellphone number is an entry point to help bolster the "emerging middle class" in countries like Kenya, the Philippines and Tanzania by giving them access to credit.