This is the sort of thing that ought to be on the "why" section of OKCupid's website.
Yep, it's the sort of thing you could leverage and get OKC to donate towards and photograph the wedding for free. No joke, I'd look in to it.
At the same time, I think word of mouth from people like me and the other happy couples is doing just fine for them. They got bought out by Match a year or two ago. I'm sure that lined some pockets over at OKC nicely. Plus since OKC is free, and plans to remain to be free, so spending money on advertising kind of breaks that business model a bit. Match however, you'll notice, is the one with the commercials and wedding pictures and what not. They are the paid service, and they bought OKC so they could have a free service that is allowed to do it's own thing.