I should have clarified. The examples were Facebook open sourcing Cassandra or Google open sourcing Android. So really the examples were Cassandra and Android.
I don't agree that closed sourced software are difficult to promote or as you say "few people share them." When people share something on Twitter or Facebook, do they ask "is this open source? then I will share" or do they say simply say "this is an awesome piece of software. let me share it"?
In contexts such as computer security and reverse engineering an open source approach gives more shares within its own community. I understand other people only care if their needs are satisfied.
I don't agree that closed sourced software are difficult to promote or as you say "few people share them." When people share something on Twitter or Facebook, do they ask "is this open source? then I will share" or do they say simply say "this is an awesome piece of software. let me share it"?