"I'm certain a hotel—more likely a brand—will take this move by Marriott and start to add a mandatory gratuity as an experiment," said Bjorn Hanson, a professor at New York University's Preston Tisch Center for Hospitality and Tourism and Sports Management. "It will likely start to happen during the upcoming peak travel season," which starts right around Thanksgiving. "But it will be a long time before there's an expectation of an automatic housekeeping gratuity or surcharge," Hanson said.
A few hotels, mostly resort properties, already add mandatory gratuities on top of resort fees.
For example, in its terms and conditions the Atlantis Paradise Island resort complex in the Bahamas notifies guests they will required to pay a mandatory "gratuity and utility service fee" of $20.70 to $65.95 per person, per day depending on the type of unit. And at the Fairmont Southampton and Hamilton in Bermuda, nightly fees including gratuities of $10.20 per person are added to most rates to comply with a collective bargaining agreement.
"In Bermuda, the mandatory gratuity is an island policy that applies to all hotels in the destination," but elsewhere, "the introduction of supplementary fees at our properties is not in our plans," explains Mike Taylor, spokesman for FRHI Hotels and Resorts.
Resort fees, which at many hotels might ostensibly cover anything from phone and Internet access to use of the gym and the pool, are already familiar to many travelers and have spread from traditional resorts to many Las Vegas hotels and convention properties around the country.
"Research suggests that people can accept a second fee," said Michael Lynn, a professor at the Cornell School of Hotel Administration, "but two or more fees and they start to get irritated. Adding a mandatory hotel maid fee is certainly not a good idea if you already have a resort or service fee."
While the conversation evolves, travelers continue to check into and out of hotels, room attendants continue to clean up after them and a wide variety of other service workers stand ready to attend to guests needs. And accept their tips.
So far, response to Marriott's "The Envelope Please" campaign has been decidedly mixed.
On Marriott's Facebook page there are a few comments along the lines of "Come on folks: tip the maids and stop complaining. It's the right thing to do." But most seem to agree with comments that claim Marriott is "trying to make consumers directly subsidize their employees' income."
Marriott International acknowledges the mixed comments and notes that it is not uncommon with many major campaigns. "But our intent is help recognize the important work of housekeepers on [a] voluntary basis," company spokeswoman Angela Wiggins said via email. "The program's just getting started, we're proud of it and we'll monitor its progress going forward."
Some descriptive phrasing around the campaign may have been unfortunate, said Lynn at Cornell, but "I don't think having an envelope with a reminder note is likely to increase people's tendency to tip."
Lynn's research on hotel tipping found that 30 percent of guests never tip housekeepers and about the same percentage claim to be unaware that tipping hotel room attendants is customary in this country. Most people know you're supposed to tip, said Lynn, but 30 percent of those people only leave a tip once in a while.
Hotel housekeepers across the United States earn a median wage of $9.51 an hour, according to Unite Here, a North American labor union that represents many workers in the hotel industry. But "because hotel guests do not always see or interact with room attendants, their hard work is many times overlooked when it comes to tipping," A Woman's Nation said in the statement announcing the new campaign.
To help hotel guests figure out when—and how much— to tip, there are a myriad of tipping tip sheets, including one from the American Hotel & Lodging Association. Etiquette expert Jacqueline Whitmore, founder of the Protocol School of Palm Beach, also offers a few tried and true pointers.
She suggests arriving at any business or luxury leisure hotel with a good supply of $1 bills, perhaps 20 or 30. "Everyone you come in contact with will generally get a tip, from the person who takes the bags out of your car to the person who takes your car and the person who brings your bags to the room," she said. "Discretely hand the person three or four dollars and thank them for their service. And in your room, tip your room attendant $2 to $5 a night."
When handing someone a tip, "don't fumble and bumble," said Whitmore, "and don't be shy about asking for change. They all have it and are happy to do that," because they know they'll be sure to get that tip.
Better yet, said Whitmore, if you're really impressed with the level of service someone provides at a hotel write a letter and hand it to the general manager, leave it at the front desk or send it when you get home.
"That letter will be shared with the department head and placed in an employee's file and reviewed when it is time to determine if someone is worthy of a raise," said Whitmore. "So your letter could have far more impact than a $2 or $3 tip."
—By Harriet Baskas, special to CNBC.com. Baskas is theauthor of seven books, including "Hidden Treasures: What Museums Can't or Won't ShowYou," and the Stuck atthe Airport blog. Follow her onTwitter at @hbaskas. Follow Road Warriorat @CNBCtravel.