You can now encrypt your Facebook activity by setting your own https preference on Facebook Account Settings page. Https is an encrypted protocol which uses encryption to secure your Internet traffic to protect it from snooping or tampering by others on the network.
To protect financial data your bank and credit card websites use this same https protocol.
Facebook says you should consider enabling this option if you frequently use Facebook from public Internet access points found at coffee shops, airports, libraries or schools. The option will exist as part of our advanced security features, which you can find in the “Account Security” section of the Account Settings page.