For Love of the Bad Boy

I just recently finished reading Motley Crue: The Dirt - Confessions of the World's Most Notorious Rock Band . Even though I usually stick to fiction, I picked up the book for a few reasons. One, I'm a big fan of the band. Two, my current WIP's male protagonist is a lead singer in a rock band, so this was helpful research. I'm not going to go into a detailed review. But I'll say that I really enjoyed the book. It was an unapologetic look into the proverbial world of "sex, drugs, and rock 'n roll." So, if you like rock music, don't mind an r-rated (nc-17?) book, and can handle the overuse of the word "dude" in the Tommy Lee chapters, then I would say go for it.

But in addition to being a fun read, this book also got me to thinking about bad boys. They show up all the time in fiction, especially in romance and YA. It's one of our favorite alpha male types both in books (and for some of us, real life). After reading this true life account of four seriously bad boys, I started to wonder why we're so drawn to them and why certain bad boys are appealing and others appalling.
The Motley members were drug addicts, womanizers, and, at times, criminals. Yet women flocked to them even before they were famous or rich. Therefore, something about them was inherently appealing.
Then there are guys like Wes on the current season of The Bachelorette. He's considered the bad boy of the show. And based on last night's reunion show, he was wildly unpopular with the female viewing audience (including me.)
So what's the difference? Where is the line between uber hot and uber jerk? What traits make a bad boy sexy instead of scary? When writing, how do we create that delicious bad boy that will make our reader not just swoon but fall in love in with the character?
I think the key probably lies in the character's motivation. Your bad boy can't just be bad for the hell of it, just because he thinks it's cool. (Yes, Wes, I'm looking at you.) You have to explore the reasons why he is the way he is with your back story. He also has to have some crack in the armor that the heroine can pry into and heal. Because, otherwise, why are we reading?
Since the Motley Crue guys maintained their appeal (in my mind) even after wildly egregious acts, I'll use them as an example of some appealing types of bad boys. (I'm leaving Mick out because he is not an alpha male.)
The "I've always been pretty" bad boy (Vince Neil, lead singer): This is the bad boy who knows he's hot. Girls have always liked him. Attention has come easily. He can get whomever he wants, which can make things boring for him. It can also lead to going through girls like they're disposable. He's not used to being told no.
Crack: He ain't that confident. Sure, he knows he looks good, but he's not convinced the person underneath the looks is all that great.
Other Examples: Eric in the Sookie Stackhouse books (a personal fave of mine), Keenan in Wicked Lovely, Jordan Catalano on My So-Called Life (to pull out an old 90s reference)
What he needs: A heroine that isn't afraid to knock him down off that pedestal and challenge him.

The "Up for anything" wild child (Tommy Lee): This guy appears to have no fear or impulse control. Seeks thrills and fun at all times. He's ruled by the Id. Doesn't take anything seriously including silly things like rules, laws, or social mores. Sees relationships as something that would hold him back from thrill-seeking.
Examples: Jules in Erica Orloff's Freudian Slip (who is basically a good-looking version of Howard Stern), Barney on How I Met Your Mother (although his thrill seeking is limited to women)
Crack: He's actually a sucker for long-term relationships. He's so passionate about everything in his life, that when he finds the right girl, he will give himself over completely to love. Tommy Lee turned lovesick both with Heather Locklear and Pamela Anderson.
What he needs: Someone that can keep up with him, but is also a calming force. A heroine who incites enough passion in him that he seeks thrills with her instead of separate from her.

The Wounded Soul (Nikki Sixx): This is my favorite to write and read about. This guy's motto is "get them before they get me". He's been hurt deeply somewhere along the way, and now has locked away all true feelings from others. He's easily angered and shuts down when anyone gets close. He can be the most formidable of bad boys because he doesn't care enough about himself to avoid danger.
Examples: Julian in Sherrilyn Kenyon's Fantasy Lover, Edward in Twilight, Jace in City of Bones, Wrath in J.R. Ward's Dark Lover, Johnny Castle in Dirty Dancing
Crack: He feels unworthy of genuine love. Nikki Sixx was abandoned by both his parents early on. So later, when people in his life showed him love, he didn't believe them. He'd push them away before he had a chance to care.
What he needs: A super tough girl that can push through that seemingly impenetrable wall. A woman that will call him out on his crap and not be intimidated by his flashes of anger. A woman that will love him fiercely.
So there's my theory. The only bad boys worth writing are the ones that offer a challenge, but that can ultimately evolve. We don't just want to read about the bad boy being bad, we want to see his character heal and reform so that he can keep the good parts (fun, attitude, touch of danger, daring) while taming the undesirable parts (lying, cheating, illegal behavior, etc.).
So, what's your opinion? Do you like a bad boy character or do you think they're overused? What makes you like one better over the other? Who's your favorite bad boy?