No one knows the full extent of the current domestic wiretapping or electronic surveillance efforts, but we know the laws are being pushed as far as possible to extend their already prodigous reach. But we also know that human nature hasn't kept the same furious pace as the electronic world, so some repetitive patterns are quite likely.
Let's just consider the pattern exercised under J.Edgar Hoover. In the excellent book, The FBI and Martin Luther King, Jr., by David J. Garrow (W.W. Norton, New York, 1981), a wiretap that began on some reasonable suspicion of attempts by the Communist Party to infiltrate the civil rights movement, quickly deterioriated. The initial probe came up dry; but Hoover refused to believe his analysts.
Hoover's pre-conceived notion that there must be Communist influence helped drag the wiretapping on for six years. Hoover's preconception, plus reliance on "evidence" by one source that was not credible (p.85), drove the FBI to tap the home and office of King and associates, and caught details of his sex life. Then the FBI, right from the top, sent an anonoymous package of the "evidence" in an attempt to force King to commit suicide (p. 126), as part of an effort to remove King from leadership and influence the civil rights movement to choose Roy Wilkins of the NAACP (p. 124) as successor to the mantle of leader.
Thus a wiretap that began with some legitimacy ended up degenerating into a power struggle by Hoover to attempt to control the direction of the civil rights movement. It was a factor in King's death. If you read elsewhere, there is a book by an English barrister in the James Earl Ray case that makes a powerful case that retired members of the FBI played a direct role in King's Assasination. Moral of the story: wiretaps could kill you, especially if you're an effective leader. This is a discussion you are not likely to find in most textbooks on democracy.