Turns out that before the Stored Communications Act, the existing law gave people essentially zero right to privacy with respect to electronic communications that were stored by a third party. The pre-existing law was basically just the 4th amendment, and traditionally you relinquish your 4th amendment protections for any documents that you give away.
What the SCA did was to create some hurdles that had to be jumped over to acquire this data. They're not quite as strong as the requirements one needs to get to obtain a search warrant or anything like that, but they're a heck of a lot stronger than what existed beforehand.
So the SCA did not, in fact, allow authorities to "seek data like this without a search warrant." Much the opposite, really.
Yes, the "third party doctrine." Really stupid stuff, especially in an age where we do almost everything over networks provided by third parties with services provided by other third parties, but our expectation is that the data we are transmitting should be as private as if we were storing documents in our home.
There is hope that some of this will be reversed, much like the supreme court ruled that phone conversations were private even though they were over third party connections, and how the SCA provides protections for things like email and (some) sever logs.
In the meantime, the government will continue to try to stretch what it is allowed under the third party doctrine without significant check.
Ars Technica had some good coverage last week of the Obama administration successfully arguing that law enforcement can request cell tower connections (giving a rough tracking of a phone's ___location) without a warrant:
The Obama administration laid out its position in a legal brief last month, arguing that customers have "no privacy interest" in [cell-site ___location records] held by a network provider. Under a legal principle known as the "third-party doctrine," information voluntarily disclosed to a third party ceases to enjoy Fourth Amendment protection. The government contends that this rule applies to cell phone ___location data collected by a network provider.
That may be true, but since we're talking about attorneys requesting information (as opposed to police seizing data), what's needed is a subpoena rather than a warrant so I doubt that detail is as relevant as the article's author may have thought it is.
"a law called the Stored Communications Act allows authorities to seek data like this without a search warrant"