FifthView
Vala
"Head hopping" isn't a problem as long as the author has a solid grasp on voice. Read through The Hitchhiker's Guide to the Galaxy or The Princess Bride, and you'll see that some scenes change viewpoint character in the middle of a paragraph, or even for just one line. Once you have your characters' voices and perceptions dialed in and clearly different from each other, it's a wonderful technique. There's a lot of misunderstanding about omniscient third, though, and since it takes most authors literally years if not a lifetime to develop awareness of voice to the point where they can shift voice seamlessly, most new authors don't use omniscient, or they try it and botch it. Botching it is when you get "head-hopping." (I also think that many fledgling authors don't understand the difference between POV and voice, but that's another issue entirely.)
The term "head-hopping" does seem to be used negatively more often that neutrally, to describe the botched attempts—often, from a perspective that favors limited third, or to describe breaking POV in limited third.
I tend to use it neutrally to describe a particular type or approach to omniscient, to distinguish that type of omniscient from others, taking my cue from this episode of Writing Excuses: http://www.writingexcuses.com/2012/03/18/writing-excuses-7-12-writing-the-omniscient-viewpoint/