Working on the sermon for this Sunday, I'm going to be preaching on the golden calf incident. Don't expect it to be a sunny message...

Food for thought on the matter.
They knew that God was right there on the mountain. Why did they rebel anyway?
They knew that God punished idolaters, as He did with Egypt; they saw Him destroy the Egyptians. Why did they engage in idolatry anyway?
They knew that God loved them, for He delivered them from slavery. Why did they betray Him like that?