If you guessed BBM, you would be correct. According to Seeking Alpha, RIM has a secret weapon in BBM in developing countries, as well as BIS. Smart phones are expensive to pay for month to month even in North America. So you can probably imagine that poorer countries, it would be a lot harder to have a smartphone. This is where Blackberries become advantageous to have.
Seeking Alpha uses an example:
With BIS, Blackberry customers pay a relatively affordable monthly fee, and in return get unlimited Internet access, email and BBM. In South Africa, for example, each text can cost a user $0.20 but BIS costs about $8 a month. On BBM, a user can send an unlimited number of messages for no extra cost. So, for 40 text messages, a Blackberry user can send 10,000 messages if she wanted.
So there you have it, if you have ever wondered why Blackberry appeals more to other parts of the world, it’s because it’s cheaper. And also because BBM is awesome.