On the other hand, there is a class of 'rockstar' developer who are actually not very good. The best way I can explain this is by giving an example.
I was hiring for a new higher-level dev, a Rails role. I was referred to a developer whos name I knew by somebody internal. I thought 95% of the task would be me convincing him to join us, and his profile was lots of twitter followers, a good following on HN and other forums, a high profile as a developer, attached his name to a lot of open source projects and spec work etc.
Turned out he knew none of the basics. He had 'C' on his resume yet he could skype chat me the simplest C routine. I asked him to scp a file up to a dev server, and he said 'I had no idea that you could FTP over SSH' - which he said after a 3-4 minute pause where it was obvious that he was googling. I learnt then that a public profile and being involved in such projects sometimes also isn't the best indicator.
