The worst headline is one that contains a factual error. Bad headlines are ones that are bland, and don't tell the reader anything specific, like 'Democrats at it Again.'
People often think that reporters write their own headlines. In fact, they almost never do. The people who do write headlines are the copy editors who are the front and last lines of quality-checking in a newspaper before it goes to print.
Headline writing is tough because often times you are given a predetermined number of spaces and words depending on the layout and the type of the story.