It's worth noting what law enforcement wishes they could do and what they can do is pretty different. The only time this has been tested in court, the Sixth Circuit said it was unconstitutional. Which is because it's blatantly unconstitutional. My money says that any other appeals court will agree, including the Supreme Court if it gets that far.
Now, the government certainly does things that are unconstitutional sometimes, and manages to avoid having any court review them. I'm sure there are abuses here. It's disappointing that the Justice Department tried to oppose a warrant & probable cause standard for electronic searches as if there's room for dispute on that one. But the minute they try to take much advantage of this law it'll be struck down, and they know it.
It's possible that I'm (weirdly) less cynical about this as a defense attorney than most people are. In my line of work the constitution is constantly standing between police and what they wish they could do. I'm thinking of a particular case, not uncommon, where a three-hour confession was basically thrown out because the judge looked carefully at the recording and the police didn't quite handle it right. They didn't beat the guy, but they didn't do what they needed to do to make sure the confession was voluntary. And of course this drives the police nuts -- the executive branch's position is always that any limitation on their power is a threat to public safety. Resisting that position is why we have constitutional standards and separation of powers in the first place.
Incidentally, the DOJ testimony[1] is a little more nuanced than Wired makes out. The testimony makes some legitimate points -- that agencies like the SEC rely on their ability to use subpoenas (as opposed to warrants) to enforce financial laws, and that it's not clear how much evidence you should need that a particular email account contains evidence of criminal activity in order to obtain a warrant to search that account. (If I have 100 gmail accounts, and you know I've used five of them to run drug transactions, do you need independent evidence to search each of the others?) This means any law governing search of emails would have to be written carefully (or vaguely, so the courts could figure it out under the Fourth Amendment). But the DOJ's conclusion that maybe the law should try to exempt electronic records from search and seizure protections is typical executive branch posturing -- both absurd and unenforceable.
(This is not legal advice. It's just a thing I wrote on a forum. I could be totally wrong. Consult your doctor if effects last more than four hours.)
[1] http://www.wired.com/images_blogs/threatlevel/2011/04/bakere..., page 11.