Betrayal is almost as pervasive a theme as abandonment. But whereas abandonment goes both ways—people abandon God, provoking God to abandon his people—betrayal is much more of a one-way street. The people betray God by worshipping foreign gods, sacrificing their kids to Moloch, classic stuff like that.
The only exception to this general rule might be when Jeremiah rails against God, accusing him of betraying/abandoning him. Otherwise, God tends to do exactly what he says he's going to do—reward obedience, and punish disobedience.
Betrayal by worshipping other gods is definitely the worst thing you can do. It's a violation of Commandment Numero Uno, but the Israelites have a bad habit of turning to other gods, starting with that Golden Calf back at Mt. Sinai. Hard to believe how you could worship other gods when the Real Deal is living in the Temple down the street, right?
There's a lot of suspicion of betrayal in the book. Everyone was pretty anxious and fearful, what with all the predictions of imminent invasion and destruction, so everyone suspected everyone else.
Questions About Betrayal
Why aren't the people able to recognize that they're betraying God? How do they view their own actions?
Is it worse when the prophets betray God than when regular people do it?
Why does Ishmael betray Gedaliah? What's the point of prolonging the chaos?