After accepting her boyfriend's marriage proposal, Sarah Nolting of Columbus, Ind., did what most modern brides do: She announced her engagement to her Facebook friends.

All 899 of them.

There was room for 250 guests at her wedding, and that meant that some of her online friends (maybe "acquaintances" is a better term) were expecting an invitation that never arrived.

"People just assumed they would be invited," said Nolting, 25, a communications specialist.

Before her wedding finally arrived in October to Jonathan Nolting, 27, a construction estimator, she had fended off a colleague who had cornered her in a conference room angling for an invitation, as well as a former co-worker who had lobbied her on Facebook.

Social media is enabling the brides and grooms to share the good news of their engagement and weddings, to post pictures of parties and other mileposts along the way. But there is a downside, and not just with the large numbers of people who in a predigital age might not have known that they stand among the ranks of the uninvited.

Couples now have less control over what information is passed on about their engagement and wedding and are being confronted with a host of new etiquette questions, from when to put news of the engagement online to who gets to post the first photo from the ceremony on Instagram.

In 2011, a Maine woman asked Peggy Post, who writes a wedding etiquette column for the New York Times, whether she should hire a security guard to deter potential wedding crashers after her newly engaged daughter had posted on Facebook, "Who wants to come to a wedding?"

Many of the daughter's friends had responded "yes" and had asked for directions, but the wedding was to be for 40 guests only.

Contacted recently, the Maine woman, who had signed her letter Mother (aka Sentinel), recalled the episode and noted that she had posted a "reply" on her daughter's Facebook page emphasizing that it was to be a small wedding and that those to be invited would receive a printed invitation.

"No uninvited guests appeared," wrote the woman in an e-mail. "I figured either her Facebook 'friends' either saw my warning or didn't have a chance to see that wide-open invitation before she deleted it." No guard was hired.

With couples sharing everything on their social media feeds, from the type of wedding cake they ordered to the bath towels on their registries, it's no surprise that there is confusion over exactly what are the appropriate — and inappropriate — uses of social media.

"We don't have a book of Emily Post rules," said Anja Winikka, site director of TheKnot.com, a wedding website, adding that the online etiquette guidelines for brides and grooms are "evolving."

For example, while many couples encourage guests to post pictures of their festivities online, creating wedding day hashtags (often a mash-up of the bride and groom's last names), Winikka said the first photo posted of the bride should come from someone close to her, such as her maid of honor. Other guests "have the green light from there," she said.

Lisa Gaché, the owner of Beverly Hills Manners, an etiquette consulting company, offered two other suggestions for brides and grooms: 1.) Refrain from posting "any details that should be privy to only the people who are invited to the wedding," like the wedding location or the band that will be playing at the reception, because it might be construed as "exclusionary." 2.) Don't post anything that could be perceived as bragging, like the size or cost of an engagement ring, or mention the registry, which might sound as though you are fishing for gifts. ◄

For many bride and grooms, though, social media has been no problem. Ethan Long, 27, a copywriter for an advertising agency, has not received any Facebook messages asking for invitations to his wedding to Alexandra Calvano, 26, a registered nurse, in September in Cape May, N.J., but wouldn't cave to pressure if he did. "If one of my friends doesn't feel included that's unfortunate, but I'm more focused on the wedding than managing people's feelings," he said.

And yet, for some of those not on a guest list, seeing the photographic evidence of what you missed is much more upsetting than just hearing about it weeks later.

"There's this 'Wow!' " said K. Cooper Ray, the owner of a necktie and apparel business in Charleston, S.C., of seeing pictures online of a lavish wedding in Los Angeles to which he wasn't invited.

"You see the room; you see the people, and obviously the only glaring thing missing is me."