This isn’t “CellularDataGate,” but it’s clearly affecting more than just a handful of people, and could involve folks paying dozens to hundreds of dollars in excess data usage for what might be an iOS bug or a bug in Apple-provided apps.
Glenn has compiled an exhaustive list of excessive data usage reports. He even mentions yours truly.
As for my own data usage, it seems to be nearly back to normal after wiping my iPhone and starting from scratch. While today wasn't a typical weekday, I used Maps, Siri, Facebook, Twitter, Safari, and even watched a little Youtube over cellular and only used about 75 MB.
As a side note, the official Twitter app is a turd. When the time comes to add more apps, the first one will be Tweetbot.
What's disturbing is that I'm using about 2 MB of cellular data at home every night, despite a strong Wi-Fi connection. However, it's a small amount of usage, so I'm going to let it slide for now.