This is an important notice for developers still using HTTP plaintext connections. On January 14th, 2014, connections to api.twitter.com will be restricted to TLS/SSL connections only. If your application still uses HTTP plaintext connections you will need to update it to use HTTPS connections, otherwise your app will stop functioning. You don't need to wait until deadline to implement this change, given that api.twitter.com already supports the recommended environment.
This SSL requirement will be enforced on all api.twitter.com URLs, including all steps of OAuth and all REST API resources.
Connecting to the API using the SSL protocol builds a safe communication channel between our servers and your application, meaning that no sensitive data can be accessed or tampered by unauthorized agents in the middle of this communication path.
Any well-established HTTP client library already supports the ability to connect to a SSL-enabled server and usually the required change is just a matter of updating a few lines of code or configuration files. For specific details about using SSL to connect at api.twitter.com, please review Connecting to Twitter API using SSL.
A "blackout test" will be performed on Jan 7th, 2014, when HTTP plaintext connections will be unavailable for a time period to be defined and announced in this discussion page and via the @twitterapi account.
If you have any questions or concerns with securely connecting to api.twitter.com over SSL, please post them here.