Sneaking into Vera Wang's bridal shop. Restricted airspace over Rhinebeck, N.Y. Closed-mouthed caterers, florists and photographers.

And unhappy friends who just can't understand why they weren't invited.

The secrecy surrounding Chelsea Clinton's wedding on Saturday is pretty tight, but one thing is certain: in this age of Facebook and Twitter, hurt feelings about the guest list are almost going to be inevitable, whether you're Bill Clinton's famous daughter or Jessica Bracken of the North Side.

The Clintons, ever diplomatic, announced that every one of the 400 or so invitees to what's likely to be the biggest social event of the year -- at an estimated cost of more than $3 million -- would be personally acquainted with Ms. Clinton, 30, or her fiance, Marc Mezvinsky, 32.

Even the Obamas are not invited.

A veteran political consultant who worked on the Clinton re-election campaign in 1996 has told The New York Times that "either you are a friend or you're not, and friends are defined at different levels."

Another longtime acquaintance noted many "noses are out of joint" from being left off the guest list.

The rich and powerful are not the only ones who agonize over invitation lists. With the way many 20- and 30-somethings spread every detail of their lives on Facebook and Twitter these days, every "friend" may expect to be included in the Big Day.

Ms. Bracken, 27, and Chris Franceshina, 26, were vacationing with friends in Greece when he popped the question. The groom-to-be changed their Facebook statuses to "engaged" that day.

"He caught me off guard," said Ms. Bracken, who works for an asset management company in Pittsburgh. "I hadn't even told my [future] bridesmaids yet."

Ms. Bracken said she tries to be discreet about posting details to her Facebook page for several reasons. First, she said, she treasures her privacy. Second, it's impolite to flaunt details of a big party that a relative few will be asked to attend next April.

"We're going to have only 150 [guests], and both of us have pretty large families," said Ms. Bracken, whose relatives are mostly in Virginia. Her fiance, an online marketer, is from Mars.

She noted that all this sharing makes it that much harder to ignore if you don't make the cut.

In the past, prospective bride and groom would start compiling their list with immediate family, add friends and co-workers, then begin cutting.

A sometimes painful process, but, at least until recently, a private one. In a world of Facebook and Twitter, the boundaries of privacy -- and good taste -- are dissolving.

"I think it is bad etiquette to be putting up your wedding details, knowing you have 600 [Facebook] friends and you are going to be inviting only 40 of them," said Erin Betler, 29, a sales representative for a contract furniture company in Brooklyn, N.Y.

In 2007, she married South Park native Tim Betler, 30, a freelance video producer and editor, and the couple have a 1-month-old daughter, Aubrey. Mrs. Betler said she used discretion in posting to a popular website, www.theknot.com, although she enjoys keeping up with friends on Facebook.

Every now and then, she said, she would run across wedding planner details on college friends' pages and think, "Maybe I'll get an invitation."

When that didn't happen, "I wasn't offended. I went through that whole wedding process and I know how hard it is [to cut down the list]. But it does surprise me, to be honest, that so much of it is about putting all this information out there."

Mrs. Betler's generation was near the front of the first widespread social media wave. She can remember a world without MySpace, yet calls her age group "more voyeuristic" than her parents' generation.

"The pressure is on," she said. "There is that sense of immediacy. When there's a wedding, they want to see [pictures of] you in the dress, walking down the aisle, six hours later."

Jeanne Hamilton has seen and heard it all when it comes to etiquette, from wedding crashers to bridezillas to out-of-control cake smashing. Although she retired last month from a career as a wedding coordinator near Raleigh, N.C., she continues to maintain the good manners website she created 15 years ago, EtiquetteHell.com.

She said she sees little wrong with guests posting photos from a wedding after the fact, if discretion is exercised. But posting tons of details from your wedding plans borders on gloating, she said. It can be tough, reading about this wonderful event most people won't be part of.

"I think it's unkind," said Mrs. Hamilton, who prefers the term "Techno-quette" for Internet manners. "You don't need to have everything on Facebook. Your life should not be broadcast on Facebook."

Handling news and photos on Facebook has become a common topic addressed by purveyors of wedding etiquette.

Should you announce the engagement on Facebook? Sure, but only after you've shared it -- in person or over the phone -- with family and close friends.

Should you give details of location and date? No, no, no. "Feelings could be hurt as friends who are not invited watch the date and time draw closer without receiving a note," says Bronwyn Timmons, a wedding blogger. "Some friends might even read into your sharing as an open invitation."

Should you include a link on Facebook to your wedding website? Again, no, no, no.

Mrs. Hamilton is planning the October wedding of her daughter, who is not big on social media. But her fiance is, and he has 1,000 "friends."

"I think there is the assumption, among a lot of his friends, that they are being invited," she said. "When they ask when the wedding is, and we don't tell them the exact date, that should be the first clue.

"I think most people can take the hint."

Doug Oster writes a blog, "Growing With Doug," exclusively at PG+, a members-only web site of the Pittsburgh Post-Gazette. Our introduction to PG+ gives you all the details.