Re: Amazon can't live without opensource
"Anyone even slightly business minded would see the logic behind their decisions"
I'm not sure I agree here. For example, Amazon are competing directly with Netflix, who open a huge amount of incredible code on GitHub (http://netflix.github.io/), and they're absolutely destroying LoveFilm. All the best developers I know would like to work for Netflix, whereas I've never heard anyone say anything positive about working for Amazon. Talks given by Netflix folk like Adrian Cockroft do a huge amount to promote the company within the wider tech community.
Netflix don't release their latest code straight away - they admit there is usually a few months between a feature going live and them contributing it back to the community, partly so they can fix it up, but mainly (I'd guess) because they don't want to be sharing their latest and greatest functionality with everyone. But they realise that tech grows old fast, and old tech isn't what keeps you ahead - it's the new stuff that counts.
From my perspective, I've had many arguments in the past against exactly this attitude - that if we wrote it, why should we give it away for free? My response to that is always the same - if it isn't our core business, what do we gain by keeping it secret? If I'm working for an ecommerce company, releasing some chef recipes or testing frameworks isn't going to give our competitors an edge, but it might attract better candidates, and if it's really popular, we might even get some code contributions back for free.
Twitter don't seem to be suffering from releasing Bootstrap, Google don't seem to suffer from Android, Guice, Guava and the many other projects they've opened - these things aren't what give them the edge.