Google is investigating the possibility of enabling HTTPS connections by default for users of Gmail, Google Calendar and other applications. The technology is already there, it s just a question of whether it will have an adverse effect on users experience. Google enables this option by default on some of its other technologies, including Google Voice and Google Health. The always use https preference in Gmail helps Gmail users (at least those who locate it) safeguard their information, but this preference only applies to Gmail sessions. When those users login to Docs and Calendar, their information flows over the public Internet.
Source: https://threatpost.com/experts-ask-google-bolster-security-online-tools-061609/72861/