A few years ago I met a 'superstar' type developer who was considered hot shit amongst the usual crowd. I met him with a view of hiring him (or, trying to) mostly because of his reputation.
I think i must have been the first person who really drilled into his knowledge, because he was more interested in talking about who he knew, projects he had been associated with etc.
I got a funny feeling about him, and asked that he do a simple code project. A week overdue later, he asks for our FTP credentials to upload it. I say that we don't run ftp anywhere, and that he needs to scp to the box. He said he had no idea that ssh can 'copy files'. urgh. He later worked out that his GUI FTP client supported SSH and got so excited about it that he messaged me to tell me about it.
I have never judged the capabilities of a developer based on reputation since.