Sadly this splendid tool is only for corporate use. Yet anyone can create his / her own account, just don't use your gmail, yahoo, hotmail, or aol account. The reason for this is that it is targeting corporate networking, adding insight and organizational charts of your company.
So a very interesting and good tool to use for you fellow employees, but it doesn't go beyond that to include e.g your customers. A way around this: give your customers a corporate email address.