Google has announced that they are beginning to give sites that use HTTPS a boost in their search engine ranking. According to Google Webmaster Central:
"...we’ve been running tests taking into account whether sites use secure, encrypted connections as a signal in our search ranking algorithms. We've seen positive results, so we're starting to use HTTPS as a ranking signal."
They go on to say that it will be a very weak boost - content is still king. We can anticipate, though, that this will become important enough that any site worried about their search rank will want to be secure by default.
Read more in the original article, HTTPS as a ranking signal.