> New ideas often seem crazy at first (e.g. renting out an airbed in your apartment to a stranger)<p>N.B. I'm currently travelling and using Airbnb almost exclusively for accommodation, if that's somehow relevant.<p>Airbnb seems to have become the cliche example of a 'crazy idea' that turns into a unicorn and, honestly, I struggle to see why people think the idea, per se, was crazy or groundbreaking.<p>It's not a crazy idea. In fact it's a very natural, obvious idea, that has existed forever. People have rented, and sub-let, rooms for decades. The problem has always been high barrier to entry (on both sides) and therefore low liquidity in the market, such that short term 'holiday' type lets are too much of a hassle to be tenable, and only longer term lets have been feasible.<p>The idea has always been there, what's not really been there until Airbnb, and what is their remarkable achievement, is the building of a singular, reputable, trustworthy, easily accessible marketplace for this, to get the liquidity to where it needs to be to be workable.<p>It's the execution on this, not the idea itself, that's the remarkable thing. If it was such a crazy idea, it would have taken much, <i>much</i> longer (+10 years perhaps) to have truly caught on. The fact that they've had such rapid growth points to the fact that a lot of hosts and travellers were ready for it and just waiting for the opportunity to take part in the short term lets marketplace.