There isn't any number your could estimate, because people are getting new connections everyday. But Dhaka has the most.
According to wolframalpha site survey, there are 556,000 internet users in Bangladesh, compared to their population of 164 million.
in 2010 France internet users are 51,879,480
In 2008 there was 15.143 million internet users.
Facebook was not started in Bangladesh it was developed in America. It is and always was available on the internet globally (unless your government blocks it).
There are about 10 million internet users in Nigeria. (2010)
As of 2007 there were approximately 42,000,000 Internet users in India.
300 users can have in 8MB broadband internet access.
How many users are now connected to nayaritenlinea.mx
a lot ...
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i watched one TV program last night. one personnel from BASIS informed that there are more than 12 lac smartphone users in Bangladesh. This is just a reference to your query. May be more than 5 lac android users are there in BD.