What makes you think they've never done it before? There's no expressed provision for privacy dictated in the U.S. Constitution. It does seem a little hypocritical.
The right of the people to be secure in their persons, houses, papers, and effects, against unreasonable searches and seizures, shall not be violated, and no warrants shall issue, but upon probable cause, supported by oath or affirmation, and particularly describing the place to be searched, and the persons or things to be seized.
So lets see to search and seize evidence and sorry as a Libertarian any interference in ones private communications from ones residence or place owned by a party has to in my view be included demands:
1. Probable Cause
2. Oath or Affirmation of the Probable Cause
3. Describing the Place to Search
Traditionally to do any sort of tap save in emergency life or death situations where there is no time for one one must get a warrant properly issued for surveillance. Such should not be hard for the government to prove in legitimate cases just go to a judge and get a suitable warrant then do the computer hack, tap phones or whatever is authorized.
As for a Judge not being trustworthy they are judges, what the hell does the government do when they appoint Federal Judges they are expected to be trustworthy. If the government has to they could have a panel of judges hand picked for such cases that have passed ample security clearances to issue such warrants.
This secretive actions by a government that are in fact OUR servants should scare the hell out of any American. Freedoms may be inconvenient to the government but that is the price of having freedoms sometimes they are inconvenient even dangerous. But the government has ample legitimate and legal tools to use all they need is probable cause and a warrant signed by a judge after a party swears to its legitimacy. If a phone company can't assist in tapping a line without a warrent then Yahoo or Google has no right to do so those cowards should be ashamed of folding to the illegal whims of the government.