By this I mean the countless hours donated by the developers to produce the Open Source software that Facebook is based upon. But I am also thinking of the music and videos 'given' to us all on YouTube.
We all use Free, Open Source software most of the time - Facebook, Wikipedia, Linux, Apache - often without knowing it. Even if many developers are now paid to work full time on their projects the vast majority of code has been a gift from its creators.
But why should they give? What's in it for them?
The 'mainstream' explanation
Normally, a sociobiologist would look for an explanation that conceivably would enhance the reproductive success of the individual and or his or her closely related group or tribe, thereby passing on his or her genes to persist in the future.
I think however with our gift giving code-culture, with no disrespect intended to any hacker or geek, such an explanation would be pushing it a bit. It seems safest to plump for a variant of kin-altruism. Here the perception of kin inspires 'bonding' behaviour within a community through the reward of kudos.
Kudos is a lovely word, it broadly means 'what is said or known about you'. Kudos is a social cement as much as ostracism and exclusion (i.e. unkownness) is a social disruptor.
Altruism such as giving, ultimate giving being self-sacrifice, has been shown over and over again to be related to kinship or pseudo-kinship (e.g. soldiers) and is statistically at its maximum for mother-child relationships.
The selfish-gene explanation of the above is obvious, especially for the mother saving her genetic copies in her child. It is postulated that groups or tribes can socially extend the idea to the survival of the group's genes, especially for a genetically related group such aher genetic copies a tribe.
So, deep breath, we are actually saying that our Open Source contributors are members of a neo-tribe and gain kudos through 'kin' gift-giving which in turn cements and supports the tribe's success.