The concern is that the feds will subpoena Google for everything they've got about everybody in a witchhunt sweep, and the results of that will be used to targe

The concern is that the feds will subpoena Google for everything they've got about everybody in a witchhunt sweep, and the results of that will be used to target individuals for further investigation based on 'suspicion of wrong-doing' rather than actual crimes being committed. Taken out of context, just about anything can be made to look suspicious.