So, this is just gambling. I'm not sure of what interest that would be here, but that is of course a personal opinion.
Many people have, and some (Roomorama, FlipKey) are reasonably successful. Heck, there's entire sub-sector of vacation home rentals (HomeAway, VayCayHero) that has publicly traded companies operating in it.
The problem with two-side marketplace is the trust. Bait-and-switch and similar scams have plagued marketplaces like CraigsList. You arrive at a place, and it's not what the photos look like. You make a reservation, and are told at the last minute that it got "flooded" a night before, and now the host gives you an option to switch to an inferior place or pay up more for a better-looking option. You arrive and find out the place is not for rent, and the photos have been taken by some scammer who thrives on taking small deposits and just repurposes same photos across multiple sites. Then it degrades into horrors like this one http://www.dailymail.co.uk/news/article-1205794/Rape-horror-...
Building a trust network and keeping a reasonably clean two-side marketplace is very hard, and is a major asset.
However, a few counter-points:
1) Brand value is critical. Look at Coke and Pepsi. Anyone can create a cola competitor, but no one can conceivably do better than these two. On internet properties, brand value is still important. Look at Priceline.com and Expedia. They still worth billions.
2) AirBnB has operational expertise that no one else has, in large part because they've been solving this problem w/ more funds and more man-hours than all of their competitors combined. More operational expertise = better service = beats out competition.
3) AirBnB is capitalized enough to buy out start-up competitors. Right now, most investors doubt someone can take on AirBnB. As such, most investors will push founders to go for an exit whenever possible.
The most valuable thing about AirBnb is the market capture. You can no longer easily compete with them because of the network effect that is now in place. Brand is irrelevant by comparison.
The competitive game is over, because they've taken the market. They were able to build from the ground up. To do what they did, now you have to take listings away from them, which you won't be able to do because of the reinforcing network effects, such as the listings, ratings, users, trust, etc.
They could change their name tomorrow morning, and it will not matter. They have captured 1.5 million listings, the owners, the user accounts, the ratings, etc. The only way to lose that, is to screw up the operational business (primarily either by really upsetting owners, or by missing a huge technology shift).
I think that's quite the understatement. But then, one could easily say this about most big brands, no? Brand happens to be really really important.
So is Coca-Cola. In most cases, a companys brand is way more important than it's technology.