TripAdvisor was one of those rare Web 2.0 breakthroughs where the power of the crowd created a viral energy all its own (and enough traffic to sell advertising).

Now Stephen Kaufer, founder and CEO of TripAdvisor, along with Dan Saul, founder of Smarter Travel Media, hope to repeat the magic in the wedding category via WeddingBook.com. By doing so, they will enter a highly competitive segment already populated by national services such as The Knot.com and Martha Stewart Weddings, and at the local level, by MyWedding.com and others.

John Dillon, a former Goldman Sachs analyst, is CEO of the effort. He told us that WeddingBook.com has initially raised less than $1 million from some angels. It can win, however, because other wedding sites don’t provide enough consumer choice since they rely on paid directory listings. The Knot, for instance, only has 16,000 listings, while WeddingBook.com has 65,000 listings.

Indeed, WeddingBook.com will list anything it can crawl or pick up via preferred wedding vendors — a valuable source that may have some conflicts because of economic entanglements, but also one that accounts for 20 percent to 30 percent of WeddingBook.com listings. Vendors can also flesh out their profile by claiming their page, a la MerchantCircle, SMBLive, etc. Eventually, they’ll be able to add videos.

On the consumer side, WeddingBook.com will gather reviews from users and provide a variety of vendor selection and wedding planning tools. Photographers, for instance, can be filtered out based on backgrounds and camera format. The site also maps vendors on Google Maps, so wedding attendees can easily map their route from the church to the hotel.

How will the site make money? Dillon said it is focusing its business model on facilitating Requests for Proposals from wedding vendors, which include locations, photographers, DJs and florists. Consumers (i.e., brides), who keep their anonymity, will evaluate proposals submitted by the site.

When consumers contact a vendor, and the vendor decides to compete for the business, the vendor will pay fees to the site ranging from $2 to $8. The system is rigged to allow vendors to say they are already booked or uninterested, etc.“You are never going to solve the problem as long as you have to pay money to publish content or to get placement,” said Dillon. “We’re taking the TripAdvisor approach to this. Our model is to give every vendor a free page and encourage them to publish as much information as they want.”

Collecting on lead fees after the fact, of course, has always been a huge problem for sites like this. How do you know who has been hired? But Dillon is confident the site will be able to collect the information, and the money — in part because vendors will be anxious to raise their reputation profile.

“It’s a pay-for-response model. … We’ll actually deliver customers to you,” said Dillon. He also noted that the site will limit the number of vendors from eight to 15 per category so customers aren’t overwhelmed. Some categories, such as wedding photographers, will have eight or nine vendors. Others might have a ceiling of 15.

“The problem is that too few vendors are contacted,” Dillon noted. The average number of photographers contacted, for instance, is four or five. “A lot of brides don’t do as much comparison shopping as they should,” he said. “As a result, they are overpaying.”

Currently, 65,000 profiles have been developed by the company from both domestic and Indian teams. More than 500 profiles are being added per day, with a large concentration on major metro markets. “We’ll have 200,000 more in a year and a half,” estimated Dillon.

But when the easy crawling has been done, “the second 200,000 will be more difficult,” he added. It will be accomplished, in part, via the rollout of an aggressive affiliate program with media partners and others.