> To me it looks like the supporters of a surveillance state did something clearly illegal for a few years, and once it started to come out they got the laws changed to legalize it,
True. And the PSP starting in 2001 was an explicit end run around FISC. Starting in 2004 FISC got involved but there were continued concerns about the legal basis ... so the FISA Amendments Act made it legal.
FISC was created as part of a mechanism to reign in potential legal and illegal activity by the intelligence apparatus: http://en.wikipedia.org/wiki/Church_Committee.