99.99% of my relevant work experience happened (and is happening) behind closed doors, and I suspect this will be true for a large majority of developers. So, not very useful.
I also tend to depend on a lot of open source projects... which means that I also find/report/fix bugs and contribute to documentation... all of which shows up in my public history.
It isn't just about relevant work experience...
I try to give back to stuff I use when I can, too, but I'd love to do much more. Time is limited, unfortunately =(