"Self" is worshiped whenever one is "selfish" (puts ones' self before others). There are many forms of selfishness. It is usually some variant, subset or combination of money (material things), power and/or appetite (appetite can include foods, drugs, alcohol and sex). All forms of selfishness can become addictive.

This is not a new idol, but is the oldest idol of all. This was the idol that tempted Satan to want to be like the Most High (Isaiah 14:14) and again when he seduced one third of all the angels (Revelation 12:4) and Adam and Eve (Genesis 3:1-7).

On the other hand, it is to this day, one of the most venerated idols.

Men are selfish by nature. This is the fallen nature inherited from Adam.

The command against selfishness is the basis for the entire law of Yahweh:

Galatians 5:14
For all the law is fulfilled in one word, even in this; Thou shalt love thy neighbour as thyself.

Observance of this command precludes Idolatry of Self.