A thing which, once started, tends to cause itself to grow
This is an index. I feel like snowball effects happen everywhere.
An injury causes abnormal movement patterns that cause more injuries.
Buying something that causes you to have to buy more things to support it. => Diderot Effect
The entire concept of Anticipatory Anxiety.
One consistent piece of structure in a personal productivity system creates hooks for others to be added. Such as a Weekly Review.
Being good at a thing puts you in a situation to do the thing more, which makes you more good at it => Success Begets Success
Economic Growth Begets Economic Growth