"The people who live in Samaria fear for the calf-idol of Beth Aven. Its people will mourn over it, and so will its idolatrous priests, those who had rejoiced over its splendor, because it is taken from them into exile." NIV translation
We see the condition of the people's heart as they do not mourn over their sin but instead mourn that their idol was taken down. Beth Aven is used for Bethel which is where the idol was set up and the name is used as a way of showing contempt for the place. We see that this heart condition didn't just afflict the common folks but also the religious and political leaders. They not only did not feel remorse at their sin but were, in fact, proud of it.
"It will be carried to Assyria as tribute for the great king. Ephraim will be disgraced; Israel will be ashamed of its foreign alliances. Samaria's king will be destroyed, swept away like a twig on the surface of the waters." NIV translation
Their calf-idol which was made of gold would be sent to the king of Assyria as tribute. Israel had made alliances in hopes of avoiding this judgment but, now, they find that this was worthless. The same type of thing is happening today as God's people put their trust in governments. In the last days, there will also be an alliance of nations that thinks they can stop the judgment of God. It didn't work in the days of Hosea and it will not work in the last days (see Revelation 20).
"The high places of wickedness will be destroyed - it is the sin of Israel. Thorns and thistles will grow up and cover their altars. Then they will say to the mountains, 'Cover us!' and to the hills, 'Fall on us!'" NIV translation
When they see that their high places are destroyed, the people will beg for the mountains to hide them from the wrath of God. When confronted with our sin, there are two possible reactions. We can turn away from them (repent) or we can try to hide. Their hearts were so hard that they wanted to try to hide. This is very similar to what we see as the seals are opened in Revelation 6.