VoIP has reduced the cost of phone calls worldwide allowing many the ability to speak with others at a low cost or even for free. Because of IP communications in fact, there has also been a business productivity renaissance. When you combine these gains with those afforded by mobility-enabling devices like Blackberries, it is incredible what has been achieved.
But there is a dark side to VoIP and it has to do with the ability to encrypt IP packets in a manner that precludes eavesdropping.
This is great from a security perspective but not great for law enforcement. Especially in Germany where Police are complaining vociferously about their inability to tap calls made via Skype and potentially other VoIP providers.
For more check out:
Register: Skype crypto stumps German cops
Inquirer: Skype baffles German plod