I can definitely see the appeal to them. We've thought about it more than once as well. The problem I've hit was being "over dressed", as in the wedding dress. One of my old BM even said if we were going to just do it, she would just wear a dress she found in American Eagle just because it matched the color scheme. It got me thinking about how everyone else would arrive. If you were invited to a backyard wedding, or were throwing one, how would you want/feel people should arrive in. I'm not talking evening wear, but at least something NICE.
Also, how would you word your invitation for the location?
Note: Because it's been brought up before, yes, it's not for another 4 years, but when you have 3 kids all under the age of 5, you honestly tell me, would you rather wait till the year out, or a few years to get things together little by little?/rant