An interesting thought, I'll bet that many companies if they had published papers or OSS for the technology they built would have advanced the state of the art today by five to ten years...
I still can't believe that back in 2001 we have been building something like a german Netflix.
Also my colleague who sat right next to me thought it would be a great a idea to have something like youtube for music in 2002 (Soundcloud) And he actually had a working service but he gave it up :)
Twitter in various forms was done about 5 times (that I saw) before the Twitter came up. Quite a few social networks predated Facebook.
Two years later, Everything launched, a year after that, H2G2, and two years after that, Wikipedia.