Even discounting the demographic issues juliawise brings up, the odds are better than that for a first marriage, because the divorce rate of approximately .5 includes successive marriages, and people who've been divorced before and remarry are significantly more likely to divorce again than people who're on their first marriage.
Recently, LWers Will Ryan and Divia Melwani (now Will and Divia Eden) were married, with Eliezer Yudkowsky officiating.
I've been to 40+ weddings in my lifetime, and this was my favorite ceremony yet. Here is the video, and below is the transcript of Eliezer's... what's it called? "Blessing"?