Either some add-on is playing tricks on me or Chrome’s developer toolbar in fact exposes HTML elements by their ID as global variables:

Here is a screenshot of an (incognito) window showing the default Google search page with some ids entered as is in the console.

I am not sure if this is really a good thing, as I really got confused why a global still was defined when it should not be, and then even having quite a surprising value…

Update: Gosh, it’s even in the HTML5 spec! First thing I do not like of this version.