Within hours of Kristen Stewart's face being planted on every news tabloid imaginable with accusations of cheating, very public apologies were issued by herself and Rupert Sanders to their significant others. This of course was a move planned out by publicists and certainly not for the benefit of those they cheated on. The damage has of course already been done and by this point I'm fairly confident in stating that neither Rob Pattinson or Rupert's wife Liberty could care less which media outlet published such apology. I know some people probably view the whole scenario as just another shining example of Hollywood romance down the tubes, but I cannot help but over-analyze the situation.
First and foremost - why cheat? If you are unhappy in your relationship the best thing to do is to separate. If you are worried about the pain you'll cause with the break up, just know that you'll cause less pain going that route than via cheating. A break up by far is classier, the opportunity to remain friends is still there, and in the end its certainly more respectful.
Secondly, and more specifically in the case of Kristin and Rob - timing could not have been any worse with filming of the next Breaking Dawn and promotion of that movie. For two folks who have to work intimately close to one another, good luck doing so now that the cat's out of the bag. Part of the allure to Twilight was their relationship both on and off screen.
Lastly, I halfheartedly speculate that Kristin and Rob may not have been a real item for a while now but have been required to emulate a cozy couple for the purposes of the Twilight film saga. I truly hope this is the case for Rob's sake. The public embarrassment is one thing, but the lying and betrayal by someone he loved can be soul crushing. Don't get me wrong, even if they had moved on that doesn't excuse the man with which Kristen chose to move on to since he's already spoken for with a wife and family. Ethics come in to play here, among other things.
"All good is hard. All evil is easy. Dying, losing, cheating, and mediocrity is easy. Stay away from easy." ~Scott Alexander