Dertonarm,
The damping does in fact damp the tonearm. It is a resistance to motion or vibration. It would change how the arm behaves dynamically.
Below is a quote from another website. This is the best summation of what is effective mass and how the distance of the counterweight (obviously in relation to the weight of the cartridge) does change a tonearm's effective mass.
"Equivalent Mass of counterweight at stylus tip=M*Lb^2/La^2(g)
If counterweight M weighs: 120g for example
Lb=counter weight centre mass distance from pivot: 5cm for example
La=effective length of arm from pivot to stylus: 24.5cm
Then "equivalent" Mass of counterweight as seen from stylus point can be calculated approx 5g.
Thus adding effective mass 5g on the cartridge+shell (when ignoring other masses of wand and fitting etc).
Effective mass is changing in accordance with the position of counterweight to balance the head mass so that "any" effective mass of arm is only "nominal or representative" value - useless for determining the actual resonance frequency expected from cartridge compliance and total effective mass (especially when the counterweight shaft is elastically connected with arm body as in "DYNAMIC DAMPING MECHANISM")."
Now to go beyond this explanation, I will add that a lower mass counterweight further away from the pivot in fact resulted in a lower resonant frequency for the same cartridge in the same arm. This gave me close to an 10Hz resonant frequency with extreme sonic benefits.
I myself did sonic tests comparing lower mass counterweight away from the pivot and a very heavy counterweight close to the pivot. I preferred the result with the lower mass weight away from the pivot. This in effect explains that the cartridge/arm type and combination is important in determining what is best.
I myself don't subscribe to the universal rule that is being put forth that the closer the counterweight to the pivot the better the performance of the arm.
Now, lets take what many people mention in regards to any of the dynamically balanced arms where the VTF is via a spring. Many suggest to disengage the dynamic VTF and use only the counterweight. I would suggest that this is more a function of the cartridge and arm combination. That in fact the best sound might result from a combination of the 2. Some dynamic VTF & some static VTF. This would yield an ideal combination in some cases. In the case of my Breuer this is easily realized. So in the end the cartridge sees the spring and the counterweight as a form of mass in terms of VTF. Effective mass can not be a defined number for a tonearm.
