As an avid participant in meetings industry conferences, I’ve heard all the arguments for booking within the block. Until recently, I’ve heeded the call.

But when I booked lodging for the recent Professional Convention Management Association conference in San Diego, the room block prices were far higher than published rates for the same hotels. In the end, Hotwire found our team a lovely property that was a quick walk from the convention center, and even had its LEED certification.

I can’t say I regret the choice, and I’m sure I’m not alone. So if a mix of guilt, residual loyalty, and old habits is the main thing keeping the room block alive, how long can we expect the practice to continue?

Doreen Ashton Wagner, managing director of Alexandria, Ontario–based Greenfield Services, believes large hotel room blocks for major meetings and events—one of the most entrenched institutions in hospitality and meetings—are on the endangered list. If they die out, she wrote in a recent blog post, “it’ll be hard to imagine a more seismic shift for the hospitality side of the industry.”

And if drastically scaled-back room blocks become the rule, not the exception, the chains will have no one but themselves to blame. “By making discount rooms available through an array of online booking sites, the hotel industry has eroded organizations’ ability to direct participants into their room blocks,” she writes. Planners have been flagging this problem for a few years, and now, some of them are going for a more direct solution.

Here’s the picture as Ashton Wagner paints it. A planner begins soliciting bids for a major meeting or trade show but specifies an official block of only 500 or 1,000 guest rooms for a citywide meeting. (This is consistent with the example one of my MeetingsNet Extra colleagues heard at PCMA, where an association executive booked a block for just 20 percent of his 7,000 attendees.)

In this scenario, the planner still expects healthy concessions on convention center rentals, arguing that participants will still book accommodations in the city. If the CVB balks at the new rules of the game, the planner moves on to a destination that will play along.

If room blocks for major meetings become a thing of the past, meeting planners will gain flexibility and eliminate a big source of risk for major events, made worse by the online commoditization sweeping the hospitality market. Hotels will lose the certainty of pre-booking blocks of hundreds or thousands of rooms.

A few more storm clouds gather when you factor in sites like backbid.com, where a hotel guest can post a confirmed reservation and get concessions or price cuts from another property. The system is fine for individual customers who are mostly concerned about price, not so much for planners who need a wider array of on-site services. It makes a certain amount of sense if you’re a small, independent hotel that was left out of a citywide bid. But it’s a disaster for hotels as a group, and another nail in the coffin for room blocks.

Mitchell Beer, CMM, is president of The Conference Publishers Inc., Ottawa, one of the world’s leading specialists in capturing and repurposing conference content, and founding chair of the GMIC Sustainable Meetings Foundation. Beer blogs at http://theconferencepublishers.com/blog and tweets as @mitchellbeer.