Although not a Mormon myself, my uncle is a LDS Bishop in Houston. He's pretty adamant that he doesn't want his daughters marrying outside the church.
Given my druthers, my son would marry a nice mormon girl, too. Just like the jewish families want their kids to marry a nice jewish boy/girl, and the catholic families want... well, you know the drill.
Point though, is that mormon kids fall in love and marry outside the church all the time, in my experience. I don't know of one though, that has been disinheirited, disavowed, disowned or "dissed" in any other way because of it.