I'm not in the US now, so this isn't on my radar 24/7 like it is for you guys back home. Below is not an opinion on whether I like this or not, but just my understanding of the legal facts.
From what I've read in a few articles, the phone records accessed were call registers. There never has been a Constitutional expectation of privacy in these; they are third-party records. US vs Miller, I believe, is the case law. With phone records, it's established that since pretty much anyone in the billing department can see the numbers you've called and the duration of those calls, you've lost any expectation of privacy.
Actual contents of your calls...wiretapping in transit of the signal...is where you do have an expectation of privacy. This requires a warrant to achieve. (A Title III warrant, in fact, which has more stringent requirements than a standard search warrant.)
Your Internet searches are likewise not private information. You willingly disclose the subject of your search (and any of your Internet activity) to the ISP, a third party, in order to utilize the service. You have to give them the URL you want to access in order to use the Internet, and this is logged, creating a record in which you don't enjoy privacy.
Mail is the same way--the contents of your communication are private, but the addressing on the envelope can be seen by many people, so you have no privacy in the simple fact you sent or received a letter from someone. What the letter says is private, unless and until it's in the recipient's hands. Then it's up to the recipient what to do with it. (Or the government, to force disclosure through a court order if recipient is unwilling to disclose.)
Basically, you have to tell another non-government person something to use these voluntary consumer products. Once you tell another non-government party something, you've lost an expectation of privacy in that information. You have no control over who the third party shares the information with, including the government. By nature of having told something to someone else, that information is not private, whether you really hoped that person would keep his mouth shut or not.
There's an inherent lack of privacy in Internet communications, whether people like it or not, or whether they realize it or not. I do see a new Constitutional interpretation on the horizon, however, as there has been in the past with telecommunications advances. There are also federal telecom privacy laws which could conflict with the government's actions, but I'm not an expert on those.
In the meantime, the SCOTUS case law is pretty clear on third-party records.