So many mobile sites implement this same unpleasant UI control where the header follows your scrolling and stubbornly takes a portion of the screen without adding any useful functionality, that I wonder if people know it's possible to scroll to the top of any page and see the header there...
<rant>I also object to menus that hide when scrolling up and show when scrolling down. I usually place the row I am reading at the top of the window to make it easier to follow visually. When I need to scroll back a little, the pesky menu comes out instead of the text. I think scroll up should be the exact inverse of scroll down, not a menu display trigger. Or, at least, offer us a few lines back scroll before showing the damn menu.
I tried to explain the retardedness of this to management, before it was implemented. They were like "but people share more when the widgets are always visible, we A/B tested this!" It's like talking to a rock sometimes.
That's like saying "but people click the ads more when they're obscuring most of the page or right next to the download button." They certainly do. Whether they intended to, however, is a different matter.