ADS-B Positives and Negatives - USA

MM wrote:

We are in the process of implementing ADS-B in Australia in every
powered aircraft from Mircolight to the big end of town.

Could you let us know the positives and negatives?

1. Cost's and who is paying for it in the USA? (i.e General Aviation,
Aircraft Owners, Government etc)
2. How is it charged, monthly, yearly or a one off cost?
3. Is ADS-B being set-up as a Collision Avoidance system or more for
Security and the War on Terror system as a watch where everyone is?
4. Could this system be used by terrorist to shoot down aircraft by
locking it the transmission from the ADS-B box on aircraft.
5. Anything else you can thing of

I see there is another good debate going on with ADS-B @ www.agacf.org
on this thread
http://www.aimoo.com/forum/postview....readID=2042329