Brett Dobbs says: "I found this the most useful guide to explain what has gone on with FISA. With flowcharts!"
1. It Eliminates the requirement that there be probable cause that a foreign target is a suspect of any kind – terrorist, criminal, ore "foreign agent." They merely need be your French grandmother, as long as they are outside the United States and not a U.S. person, and if the government says wiretapping them is for the purpose of collecting "foreign intelligence information" (e.g., her Pommes Frites recipe)
2. It requires the cooperation of telecoms in these efforts
3. It eliminates of the need to specify a particular email address or phone number to be wiretapped
4. 1-3 together imply that certifications of wiretapping on individuals is not the issue. The point is to use telecom cooperation to target large collections of data on communications between U.S. Persons and foreigners. This implies data mining – where, for instance, because a foreign target has communications passing through a given domestic switch, any communications (domestic or international) passing through that switch are subject to collection, analysis, and storage. There are "minimization requirements" meant to ameliorate this, but it is unclear if they really help.