Researchers: LinkedIn’s built-in efforts to expand the social networks user base are at risk of over-sharing. They say LinkedIn assumes that if an email address is in your contacts list, that you must already know this person. With any luck and some imagination, you may well be on your way to an A-list LinkedIn friends list (or a fantastic set of addresses for spear-phishing, stalking, etc.) Researchers say they found several hundred possible addresses in a few seconds using a Microsoft Excel macro.”]
Source: https://krebsonsecurity.com/2014/09/linkedin-feature-exposes-email-addresses/