Yo-yoing in a paceline is one of the most common newbie mistakes and drives everyone crazy. It actually drives me insane when someone gets their turn on the front and surges ahead by increasing their speed as soon as they get there. That won't really help things and will just tire the entire group. In race situations, we've usually told the person a couple times and if they still fail to do it, we'll just ramp it way up right after they take a pull. They usually get the message if they're able to latch on again.