It's real and happens once in a while. It tends to happen more frequently during heatwaves when everyone will likely be running their AC and putting major strain on the grid. Last September I think there was a 3-hour OhmHour (kind of an oxymoron but ultimately it means more potential points).
Yesterday (7/23), I had a 7-9PM one, and today (7/24) I have a 6-8PM one. Can be pretty brutal in the heat, but if you plan around it, you might be able to score some free AC while you're out of the house. I know I plan on heading back to the office tonight after I eat dinner and flip the breakers since it's only a couple mile commute. Get OT, free AC and as many possible points as I can get from the OhmHour!