I agree with Kathy Sierra's argument that employers need to worry less about finding employees with a passion for their company and more about finding employees with a passion about their work. Having a primary passion for your work means you'll always look out for the interests of it and its users. In the long run, that will be in the best interest of your employer (since they commissioned your work in the first place). The opposite doesn't always hold true--having a passion for your employer above your field and profession can sometimes result in choices which are detrimental to your work (and thus, in the long run, detrimental to your employer).
Things get more interesting when an employer provides the freedom to take your work with you. That's what open source licensing does. If you're at Microsoft, I hope your primary passion is for general fields such as operating systems or GUIs. Because you certainly won't be able to take any of your specific project work with you some day when you walk out the door. But at a company like Sun, that's not the case. You don't have to be afraid to put your full passion into our application server project. If you leave some day, you'll still have full access to the work that you and others have put into your project, plus the option to continue contributing (or fork it and start your own competing effort, if you think the original has gone far off course). The same is true in areas such as operating systems, programming languages, and even hardware. Instead of "passion for your work" having to remain at an abstract level, it can be at the level of specific projects and efforts. That's a good thing.
I realize that Kathy had a bad experience working at Sun (and she even infers that Sun is an example of "what not to do" in one of the comments following her post). I don't know any further specifics of her situation, but I do think it's safe to say that Sun has evolved in this area (and continues to do so). As a recent European Commission study shows, Sun is the world's leading open source contributor. That's a big change. And in this context, I think it also means a big change in how the company thinks of its employees' work.
When talking of allegiances, some people say "love it or leave it." Perhaps a better saying would be "love it because you can leave it." That's a good measure of freedom and values in any setting. And in the setting of tech employers, I think it's a measure that Sun is leading.