While planning my wedding, I once joked about eloping in front of my mother-in-law. I made it totally obvious that I was joking, but she didn't stop bitching for the next two hours.
I agree, a couple thinking about eloping should put just as much effort into planning their married life as a couple thinking about a big wedding with a big poofy white dress, marching armies of bridesmaids and groomsmen, and a few thousand of their closest friends in attendance. Eloping is often equated with spur-of-the-moment (Britney) while big weddings are often equated with serious commitment, however
this does not hold. I know people who eloped and are still happily married years later; I know people who had big weddings and are now divorced.
Under what circumstances should a couple elope? If they want to, or if they know they want to get married and build a life together but need to get it on paper in a hurry (e.g. for immigration purposes) or they can't afford the big fancy wedding. As for having an official ceremony later, sure, if and when they want to. It is (or should be) up to the couple.
Hybrid Mode
