Seems Twitter has been listening to their user community regarding HTTPS. May also have something to do with the Firefox plugin Firesheep security issue (which I posted about back in November of last year), which automatically steals (using sidejacking) session cookies. If HTTPS is enabled, Firesheep (and sidejacking) will not work. Twitter has started switching users to HTTPS by default.
A tweet from the Twitter.com PR page tells all. Most people who use Twitter, don’t realize that you can type in https://twitter.com, which provides you with a significantly more secure connection, especially when using a public wireless network.
Worth noting, HTTPS doesn’t currently work with your mobile browser, so you will still need to go to https://mobile.twitter.com to use HTTPS. Twitter is apparently working on a solution whereby you will be able to use the HTTPS setting on both twitter.com and mobile.twitter.com. HTTPS is already the default in its official Twitter for iPhone and iPad applications.
Other third party Twitter apps (i.e. TweetDeck) may or may not support HTTPS, so I suggest you first check with these Twitter app developers before downloading and installing.
Safe surfing folks!