> I suppose they could do something like, if one person keeps "finding" the same images, then maybe look into it.
You're still missing an important implication of this, now a real child pornographer's lawyer can get him off by creating enough doubt in Jury's mind that Geek Squad's employees planted the evidence, especially since they are getting paid for it.
In other words, not only there is a risk of innocent people getting arrested and possibly going to jail, there is a risk of guilty people going free.