Amanda Knox was not freed on a technicality. The only technicality was that there was no evidence against her or Raffaele, the only evidence that had existed having been shown to be fabricated by the police and prosecution.
I think there are a lot of cases like this. The police 'know' who committed a crime, so they frame that person. In general, they frame a guilty person, and so not much more is heard about it. One example is OJ Simpson - although he was guilty, he was acquitted because some of the physical evidence against him was planted by the LAPD. If he hadn't had such good lawyers, he would have gone to prison for the crime which he did commit.
In this case, for whatever reason the police decided that Amanda and Raffaele were guilty, so they tried to force confessions out of them, and then planted DNA evidence. By the time they found who really committed the crime, they had too much invested in the case against Amanda and Raffaele. They couldn't let them go after initially finding so much 'evidence' against them. So they went to the other extreme and talked up their participation in a Satanic sex party gone wrong.
As Bubbaluv said, the Patrick Lumumba allegations were suggested to her by the police during an interogation designed to break her psychologically. The defamation charges are just revenge on her for having shown up the Italian justice system for the sham it is.
All very sad. The fact that she is young, American and photogenic isn't why she was acquitted. But it does indicate that the might be dozens of old, nonAmerican, or nonphotogenic people in prison who are just as innocent.