UAVs - a growing midair concern?

Recently I've seen articles talking about the use of Predator UAVs (66
foot wingspan, 10,000 pound MTOW) along the US-Mexican border
(http://www.popularmechanics.com/scie.../4213464.html), as well as
tests of smaller (10 foot wingspan, 44 pound MTOW) UAVs by the Houston
Police (http://www.popularmechanics.com/scie.../4234272.html). Now
there's news of an even smaller (6 foot wingspan, 4 pound MTOW) UAV
for use over forests (www.sacbee.com/111/story/836413.html).

Given an apparent increasing use of UAVs in areas where we wouldn't
expect to find one, what should glider pilots know about avoiding
midair collisions with UAVs? Obviously the UAV operator/pilot isn't
going to see us. Will a transponder/PCAS/ADS-B help us detect/avoid
UAVs? Will the use of UAVs in police operations/drug surveillance
require a NOTAM, considering that could tip off the bad guys? Will
there be strict altitude adherence by UAVs? What about ridge flights,
where a 4 pound UAV at 250 feet could pose extreme danger to a glider
traveling at 100 kts?

Can someone educate me on this subject?

-John