...colnago, the N900 only has an option to add Skype usernames to a Contact, either to Skype call or Skype IM that user. For phone numbers, it makes a new button when selecting the contact (but not entry to edit in Contact details) with the same details as the regular phone numbers. While other Skype clients allow saving phone numbers, the N900 already has a way to store a number for a contact, so it is using that instead.