So either the informants (at least one, and likely all three) lied to the FBI under penalty of perjury, or the FBI agent getting the warrant perjured himself to the judge. Or both.
While it's clear that the Geek Squad agents are obviously acting as paid officials of the FBI in this case, they did not, even if they lied, commit perjury in any form. Just a claim from an anonymous tip can be enough to get someone's house searched and it'll stick in court. Even if the anonymous tip was found to be inaccurate. The police love tips that allow them to search the property of people whom they're interested in. The warrant has to be specific, but they can pick up any evidence of other crimes so long as the original warrant reasonably covered the area where the actual evidence is. I'm not a huge fan of this policy, as this is how the DEA and whatnot fake an evidence chain, but it is the way it works. The courts have operated this way for some time. You'd need a brave judge or some legislation changes to change this.