Larry Page and Sergey Brin brought in a new age of founder control over companies in Silicon Valley. Is their departure a symbol for the end of an era? (GOOGL)

Alphabet CEO Larry Page and President Sergey Brin announced that they were stepping back from managing Google's parent company on Tuesday, ending a 21-year stretch of founding Google, growing its ecosystem of products, and later managing its parent company. Among other things, Page and Brin are widely credited for kickstarting a new age of corporate strategy in Silicon Valley, by ensuring that they always held voting control within the company that they founded. Other founders drew inspiration f...