Combine seven ideas...

1. On the Internet nobody knows you're a dog.
2. Any sufficiently large user base will reflect the population as a whole.
3. Every civilization has criminals.
4. It's hard to separate criminal thought and speech from lawful thought and speech.
5. You want to protect liberties for everyone even though some people abuse them.
6. Every nation interprets right and wrong differently.
7. Skype serves 200 million people in more than 100 countries.

That said, see this investigation, Paedophiles use Skype ‘loophole’ to woo children, by Daniel Foggo, Claire Newell and Martin Foley of UK's The Sunday Times dated 6 May 2007. They primed a honey trap with Skype user profiles targeting pedophiles seeking sub-14-year-old girls in locales convenient to their investigation. Sure enough, creeps fell for the bait.  

Skype isn't a bulletin board where moderators can watch for bad behavior. It's a private, encrypted, person-to-person phone system. So Skype's ability to intervene before something bad happens, or even to detect that something bad has already happened, are very limited. As Kurt Sauer, Skype’s chief security officer, told the Times: “This raises some very practical issues. However, we have not found a way to address each of the issues.”

The very efficiency of Skype's directory is what enabled the bad actors to locate their targets. Millions of people use that efficient white pages to find and talk with each other daily, allowing Skype Journal and other reporters (like the ones at the Times) to investigate stories all over the world. You don't want to cripple an entire network as a response. What can you do? What are your options?

There are matters of call content. What do you do when the age of consent in one jurisdiction is 18 years' old and is 14 in another? When the definitions of predatory behavior, fraud, or snooping are different? When a call can be described as patriotic whistleblowing, industrial espionage, or treason, depending on your point of view, in the same country?

The problems aren't simple. The solutions aren't obvious. Kurt's going to earn his pay architecting policies that work.