The erosion of privacy began well before 9/11
It actually began in the 80s
Naturally, the precedent set in place in the 80s really came full circle under the Patriot Act, which expanded it significantly. In both the Bush and Obama administrations this would come to expand to many more things, including ISPs and internet communications companies among many others.
An NSL asks for a company to hand over their records and can be as specific or as broad in their demands as they want. Again, there is no judicial oversight at all, and on top of that there is a gag order. The only people who are allowed to be consulted are attorneys. The attorney is then also bound by the gag order. Only people within the company who are necessary to notify in order to comply with the NSL are likewise allowed to know. No one else in the company may know, and anyone who does is likewise bound by the gag order. They cannot inform anyone at all, and really the only way any company has fought back is challenging it in court. There seems to be a lot if differences in opinion within the courts right now and unless the Supreme Court hears it, this will remain in place.
Here is the kicker though...Who allowed Congress to pass these laws that have given such unprecedented and easily abused powers to the Executive Branch in the first place?
None other than good old Ronald Reagan. Yes, Reagan was the one who got the ball rolling on the erosion of privacy and thanks to his administration it has now come full circle. So next time you hear of how Bush/Obama was/is supposedly removing our Constitutional rights and overstepping their bounds, remember that it all had its origins in the Reagan administration. That administration created the problem which resulted in the loss of our civil liberties and rights to privacy. It has only gotten worse since then.