In defense of data slurping
If X is a mobile phone use, and all calls to and from X and all base stations connected to are logged, when X turns up dead those logs can be examined and may help reveal clues as to the murderer or the reason. I don't think many would have a great problem with that per se.
Likewise when X turns out to be a terrorist, who they are involved with might be determined through those logs. Again, I don't think many have a great problem with that.
But how are authorities meant to provide such benefits other than by logging everyone?
And it is, thus far, simply logging or 'slurping' but not spying as such. The problem comes in how and when logged data is used which may then amount to spying on some level.
It is false though to say data slurping is of itself spying. Asserting logging is spying and arguing the slurp should not happen is usually a brute force approach to attempting to prevent perceived misuse of the data later. It is a doomed approach because there are legitimate grounds and beneficial reasons to log and slurp (as above). Those who want to stop actual spying need to move on from saying the part which isn't spying is spying. They're fighting the wrong battle.
I am happy to hear arguments why there should be no logging at all despite any benefits that may have; just don't call meta data logging spying. I am against the misuse of logged data and what does amount to spying. We do need to be sure we have nothing to fear from our logged data unless we do turn up dead, are involved in terrorism or other criminal activity.