That's why I stated "when needed". I thought I didn't have to explain it in more detail, but it seems I do. You obviously have an interest in these things and rightfully have issues with pure MP arguments. In this case you read something into my comment that wasn't there. That's my despair, and one of the reasons why I try to avoid commenting on technical posts.
Note that I also stated that I did understand that there were other technical reasons. My comment was limited to the question of bandwidth only.
My original question that you didn't reply to still remains. From a pure bandwidth point of view, they could crop the image when they need a high transfer rate so that they can have a higher resolution when they have enough available bandwidth.
If they chose 2MP for other reasons, that's fair enough.
I don't think you quite understand the difference between cropping and compression. Cropping an image is the equivalent of choosing which part of the image Facebook displays as your profile picture. While this method could reduce the size of the image to transmit down to '2MP', there's really no purpose in taking photos that are essentially cut in half.
Note that I also stated that I did understand that there were other technical reasons. My comment was limited to the question of bandwidth only.
My original question that you didn't reply to still remains. From a pure bandwidth point of view, they could crop the image when they need a high transfer rate so that they can have a higher resolution when they have enough available bandwidth.
If they chose 2MP for other reasons, that's fair enough.