Google gives you the email addresses because you provided them with that data, it's yours to begin with. Facebook will give you the email addresses, but only for the users that allowed it to share that data with you.
Will Google give you the email addresses of your Google+ contacts, if they decided not to share their address with you? I doubt it, and rightly so.
“Data Liberation” means that you own your data, not that using some social network gives you the right to be able to communicate with people outside of that service. If you want to contact them outside of Facebook, ask them their email. It's your problem, not Facebook's.
Your argument is like saying that Google should give me my Gmail contacts' phone numbers, so I can contact them without using email.
Google gives you the email addresses because you provided them with that data, it's yours to begin with. Facebook will give you the email addresses, but only for the users that allowed it to share that data with you.
Will Google give you the email addresses of your Google+ contacts, if they decided not to share their address with you? I doubt it, and rightly so.
“Data Liberation” means that you own your data, not that using some social network gives you the right to be able to communicate with people outside of that service. If you want to contact them outside of Facebook, ask them their email. It's your problem, not Facebook's.
Your argument is like saying that Google should give me my Gmail contacts' phone numbers, so I can contact them without using email.