I've heard of that too, but it is not actually true. Under the Patriot Act, a search of persons or premises still requires a warrant issued by a judge.
What you may be referring to is the "National Security Letter" that agencies like the FBI can issue which requests information from third parties, like credit card companies. It has nothing to do with searches of premises.
As far as third parties go, perhaps there is a privacy argument that should be made. But then again, this is information that I've already allowed some third party to keep about me. It is my definition already *not* private. But there is some discussion that might be worthwhile about this.
The horse's mouth.
"Under the Patriot Act, a search of persons or premises still requires a warrant issued by a judge."
Secret warrants, issued by secret judges, concerning secret material, served by secret LEOs, and if the subject of the warrant finds out, somehow, that they were served and doesn't keep it secret, automatic prison. That's the problem I have with the Unpatriot Act.