I have been looking at the blank theme and find lots of selectors of plain elements like h1, h2, h3, p, ul/li, a etc etc..
I assum that there is a good reason for this!(?) but I fail to see it.
I would say that it is best practice is to never target id´s or html elements and this should be changed in the themes provided by magento.
We can make it work but this will force us to use bad, ugly selectors and in worst case !Important (nooooooooo!!)
So, please magento, don't hurt us like this!