What inspired this wish list request? We often work with large data tables (1e5-1e7 rows). Sometimes we want to scroll up a bit, but the scroll bar at the right is hard to reach, and in large tables if you even touch it the view moves by thousands of rows. So we're stuck with the arrow keys or pg-up/pg-dn which is clunky.
What is the improvement you would like to see? This is a feature we have implemented in a home-grown tool that became incredibly popular. The idea is this: in a data table, you hit (or hold down) a button, e.g., the mouse-wheel button, and then from wherever your mouse started, dy = (current y-pixel of mouse on screen) - (start y-pixel when button was clicked), then the scroll-rate is pow(dy,3)/100000 rows/second. I recommend only scrolling in one direction (vertical vs. horizontal, maybe based on the angle of the drag).
Why is this idea important? This feature will enable smooth scrolling of data tables from very slow to very fast with small movements of the mouse, and enable users to navigate quickly through their tables.