It isn't "Mole-skin" and it isn't "Mole-skine", the "correct" pronunciation is actually "Mol-a-skeen'-a". It's Italian....
The company does say there is no "correct" pronunciation and that any old way you pronounce it is just fine with them (which is exactly what I might say were I selling the things!)
This video is offered for example:
The Moleskine image was originally posted to Flickr by Sembazuru at http://www.flickr.com/photos/sembazuru/6974372/ and is used under a Creative Commons license.