Brian Krebs writes:
One of the risks of using social media networks is having information you intend to share with only a handful of friends be made available to everyone. Sometimes that over-sharing happens because friends betray your trust, but more worrisome are the cases in which a social media platform itself exposes your data in the name of marketing.
Read more on KrebsOnSecurity.com to find out more. LinkedIn notes that they are not unique in inviting users to share their contact lists, but are planning to implement changes to give users more control over the discovery of their email addresses by others.