Stephanie Kahn wanted to bask in her engagement for a few hours before diving into the task of calling aunts, uncles and good friends with the big news. And even before she could call them, she had a surprise party to attend, one that her fiance had set up for their parents and her "closest group of girlfriends." That party was when Kahn lost control of her news. Some of the guests took photos and were "uploading them on Facebook before I could even post anything," Kahn said from Smyrna, Ga., where she lives. "Of course the next morning I...