The US National Security Agency apparently played a major role in the arrest of 9 folks in Britain and 1 in Canada on charges of planning a terrorist act and belonging to a terrorist group. The key: an intercepted email message:

“That’s the first admission I’ve actually seen that they actually monitor Internet traffic. I assumed they did, but no one ever admitted it,” Mr. Farber said.
Officials at the NSA could not be reached for comment. But U.S. authorities are uniquely positioned to monitor international Internet and telecommunications traffic because many of the world’s international gateways are located in their country. And once that electronic traffic touches an American computer — an e-mail message, a request for a website or an Internet-based phone call, for instance — it is routinely monitored by NSA spies.
“Foreign traffic that comes through the U.S. is subject to U.S. laws, and the NSA has a perfect right to monitor all Internet traffic,” said Mr. Farber, who has also been a technical adviser to the U.S. Federal Communications Commission.

Uhhh, no they do not have that right and to the extent that there are laws allowing this behavior they need to be severly curtailed if not eliminated. There is too great an opportunity for abuse and, at minimum, these searches should not be allowed without probable cause. This does not appear to be the case at NSA.
Frankly, I would have expected Farber, who sits on the board of the Electronic Frontier Foundation to express a little more concern about this.