So far technological improvement has happened on a global scale. The planet is the most impressive self-improving system. There are also local self-improving agents, like Google, Apple and Facebook - and the government. These are the most powerful kinds of self-improving systems we can see. I figure those systems are closest to taking the intelligence explosion to the next level. Again, from this perspective, the "lone-programmer" model seems very unlikely.
Link: aleph.se/andart/archives/2011/02/why_we_should_fear_the_paperclipper.html