On the 21st of January Skype corrected a vulnerability in their call/instant messenger software that could have allowed a malicious user to discover the IP address of a person of their choice using the victim’s Skype ID.
To prevent this, Skype have changed a default setting within Skype to hide your IP address from potential attackers.
Skype recommends that you install the latest of Skype to benefit from this change. An updated version will be available soon to address this for Skype when installed on an Apple iOS device.
This issue was previously discussed at length in August 2013 in a blog post by Kate Russell. Moreover further discussion of the issue addressed by Skype within this update is available within this blog post by Graham Cluley.