The book I'm reading now (which I won't name because I'm using it as an example) has a TON of head-hopping. The bad guy, the guards who guard the bad guy, the kid, the hero, the heroine, her dead husband's best friend, the maid, the innkeeper, EVERYONE has a point of view in this story. It is driving me crazy to read it because I can't keep all the points of view straight and I've had to go back a paragraph or two every time we switch to see whose thoughts I'm reading. (Because there is NO warning that we've switched. Ever.) So confusing.
Not only is this difficult for a reader, it also distances the reader from truly experiencing the story. I can't get close to the heroine's thoughts and identify with her because I only get a paragraph or two of her before we're thrown into her maid's thoughts and then the villain's thoughts. I really want to get to know her and her reactions to the conflict and I can't do that with a paragraph here and a paragraph there.
It also makes it difficult to go beyond surface emotions when the hero and heroine aren't given top billing. How can the hero express any real emotion or turmoil when he's barely given two or three minutes on the page? It doesn't do the story justice. (And this particular book has a good story, but a terrible delivery because of the head-hopping.)
So, my soapbox today to writers is, please don't head-hop to every Tom, Dick, and Harry in your book. Give yourself time to explore the hero and heroine's feelings, emotions, and reactions. Don't shortchange yourself or your story by trying to cram everyone's point of view into the book. Stay with the ones who matter so your readers can come to care about your characters and what they're going through. You don't want your story to feel like you're trying to tell your best friend what's going on in your life, only to have fifty interruptions until you finally give up.
Point of view is integral to a good story. Use it wisely with only those who need to have it to tell your story in its best light.