Q: How far does a character need to move to be considered running for the purposes of A) making a running jump, and B) making a charging attack?[spoiler=Physics Breakdown]
To provide some real world examples, look at
this and
this article examining acceleration and the human body. Physically, at least, the fastest acceleration attainable is 9.8m/s; although the book indicates a falling rate of 50m in the first combat turn, followed by 150m in the second, and a terminal velocity of 200m per combat turn (240km/h, which is a little less than real world skydivers can attain), realistically this will be much less. Usain Bolt managed to clear the first 10 meters of his record setting 100m dash in just 1.685 seconds; in other words, going from 0 to 5.935m/s in one second.
Using equal scores for Agility, Body, Reaction, and Strength, and assuming that a trained runner could get maximum hits allowed by physical limit, this would put Usain Bolt at just below an attribute rating of 3 in Game Mechanic terms:
3 AGI/BOD/REA/STR gives a base running rate of 12m
Add an additional 8m from sprinting (Physical Limit of 4 x2, assuming 4 net hits)
For a total sprinting rate of 6.666667m/s (20m/3 seconds).
The fastest man of the modern world, then, can accelerate to 21km/h in just over 1.5 seconds, whereas in the world of Shadowrun even a complete weakling (1 in all physical stats) can manage to hit nearly 10km/h in just 1 second.
Interestingly, an AGI10 BOD/REA/STR 6 character with Running 12, Hydraulic Jacks Rating 6, and using Edge 6 to get rule of Six on 30 dice (Run rate of 40m + (Sprint = Physical Limit of (16+6)*2 = 48m)) could reach speeds as high as 88m/second (an astounding 316km/h, or, if using the more conservative 3 second combat turn measurement, 29m/s or 105km/h); such a character would be surpassing the modern day cheetah in terms of acceleration by a factor of three (and possibly breaking the laws of physics in the process), and demolishing it's maximum speed as well.
With the current rule of having to exceed walking rate, I am imagining an Agility 10 character doing a warm up lap, running 10 meters away from the enemy just so he can turn around and charge 11 meters back (effectively counting as running).

As Agility directly impacts how far a character can jump it makes sense to require that a character attain a certain speed for the purpose of a running leap, but a charge move seems to be all about acceleration in order to increase momentum and thus the force of an attack.
Since even the slowest character can achieve a running speed of 4m/s in one action phase, it seems odd to penalize high-agility characters who could potentially achieve as much as 40m/s speeds in one action phase.
Given that an increase in velocity results in an equal increase in momentum, even the slowest character moving at 4m/s can attain a quadrupled momentum which in effect quadruples his/her mass (a 60kg character impacting with a momentum of 240kg-m/sec in the direction of movement). The faster character in effect multiplies his/her momentum by 40, which could lead to potentially catastrophic consequences (imagine the same 60kg character sprinting at a rate of 40m/s, effectively impacting with a momentum of 2400kg-m/sec in the direction of movement). By comparison, a 100kg linebacker in the NFL can hit approximately 35km/h, meaning that if he was to hit an immobile target he would impact with an approximate momentum of 980 kg-m/sec.[/spoiler]