The rumor is that the United States, with its European and New Zealand partners has a global servellence network that monitors all telephones, faxes, etc. While Echelon can be dismissed as paranoid rantings (because lots of paranoids rant about it), an unexpected number of reasonable people are also concerned about it.
One of the theories is that laws preventing internal monitoring can be circumvented with Echelon. For example, the NSA would like to monitor communications within the United States in order to track terrorists. However, they are barred from doing so by law. However, they can invite the Britsh to setup monitoring stations within the United States. Presumably, they would tell the British about important stuff they monitor if they would do likewise.
