Dave,
I could argue both sides of this program, a good part of me sees this as a huge intruson. I certinally felt that way when the Bush Cheney gang originally set this up.
I was surprised that President Obama did not curtail this practice when first elected. I have given this a good deal of thought and this is what I have come up with.....
To have immediatly stopped this program, Obama would have been painted by the right (Cheney and the old school Republicans) as nieve and not up to the job of protecting America. (of course he was anyway)
Additionally any successful terrorist style attack that would later be traced back to the internet, the right and the people would NEVER stop condeming him......
Another thought, when Obama did not immediately stop this program, I though perhaps when shown the data, the type of folks and plots they were watching he could see the need to continue.
Dave, it seems that we know of several devious plots have been stopped and its entirly possible that we don't know all the successes. But rest assured we would know of any failures.
On top of that, how many plots were never started because they know we are watching?
Now about this most recent deal with the car bomb at the airport, if the co-conspiritor was another terrorist and not a US agent, we might just have had many, many deaths and a perminant disruption at all airports (searching every single car forever)............thats an intrusion too.