But here's the thing about Us. People often lump them in with other gossip rags like Star and Life & Style or even the National Enquirer, but in reality they are very different. I used to be an avid Us Weekly reader and believe it or not, they are pretty damn accurate. 90% of stuff they print has more than a grain of truth to it, so although I don't completely buy the KB cheating thing right off the bat, I suspect there is some validity to it and that's why her rep felt the need to address the rumor. Us Weekly is powerful and pretty well respected for a gossip mag. It also has a huge amount of readers, so what they print tends to stick, and like I said, they don't usually print stuff they can't back up.
ITA. Back in the day when you could get really cheap magazine subscriptions off Ebay, I had one for Us and since I ride public transit, I always had an Us in my purse. I would know about celebrity breakups and drama for months before publicisits "confirmed" that there were "irreconciliable differences." Now... that's not to say that Us doesn't run its share of PR fluff pieces a la People, or that it doesn't get things wrong. But I don't discount any tabloid, not even the Enquirer - they were the only ones that had the guts to print the John Edwards story - years before he himself went on Oprah and admitted everything.
In fact, if you want to know the truth, the only mag I don't believe is People!

Let's play a game. If you were a publicist representing two actors that were dating and they broke up, how would you "publicize" it?
A) You could release a short statement to the media, asking for privacy and saying everyone remains friends, or
B) You could orchestrate competing "he said / she said" stories about the breakup, in order to get more headlines and chatter about your respective clients, while still clouding the issue of what really happened but still publicizing a break up. Ex: She said, he wouldn't commit and he's an irresponsible jerk. He said, she cheated. She said, I have to focus on my next project {insert project here for publicity}. He said, I have to film my new movie {insert movie here for publicity}.
Just a thought.