2. The most usual cases where speed matters are two and three base advances--double, triple, second to home on a single. I'd think the advantage would diminish in proportion.
Rather than paraphrase, here's the relevant paragraph from the official rules:
"Any runner is out when he runs more than three feet away from his baseline to avoid being tagged unless his action is to avoid interference with a fielder fielding a batted ball. A runner’s baseline is established when the tag attempt occurs and is a straight line from the runner to the base he is attempting to reach safely."
That's from 7.08 (a) (1).
I can't see any way this rule could prevent them from following the theory in this article - possibly it might be problematic if the tag attempt occurs while he is still right near his original base (or home plate), but in that case he would surely be tagged out anyway.