It's also a critical ingredient for failure.

I'm a huge fan of "necessary but not sufficient" qualities like this.

A startup needs:

1) Boldness 2) A crazy idea that most people think is stupid. 3) Persistence

All of these things seem to be absolutely required for success. But none of them is sufficient. Combine 'em with good "product/market fit" (a la Andreessen) and I think you win.

Startups don't need "A crazy idea that most people think is stupid". In most cases, an idea that most people think is stupid is exactly that.

Startups need to offer something of perceived value, that's pretty much it. In some cases, it's doing a typical task in a non-typical way, or doing something non-typical altogether (your crazy idea), or marginally improving your typical task in a very typical way.

In the end, it's all about value.

I disagree. If everyone knows that an area is an amazing opportunity, then it's probably not an amazing opportunity. Every single runaway success at some point had a whole host of people saying, "That's ridiculous-- it'll never work" on some level.

examples:

1) When google was on its way up, it was a well-understood fact that no one could make real money on search. Oops.

2) When Excite was getting funding, everyone told them that search was dumb. People would do 1 search and bookmark what they cared about (and would never search again).

3) The very idea of youtube (giving away tremendous piles of storage and bandwidth) didn't seem very smart to a lot of people. Plenty of online video startups had failed.

4) Blogger couldn't get more funding and had to lay off their entire team.

5) If I described twitter to you 3 years ago, would you have been blown away by the idea?

6) Salesforce.com was not exactly warmly embraced by the enterprise when they first launched.

7) Marc Andreessen said he was constantly stonewalled by businesses when selling them stuff at Netscape. "The Internet? Inside our network?! MADNESS!"

Hindsight make these ideas seem obvious-- but at the time, they were pretty ridiculous.

As you say, most ridiculous ideas ARE really ridiculous. Thus the "necessary but not sufficient" part.

My point wasn't that seemingly ridiculous ideas never succeed, it was that they are not a requirement for startup success.

Startups - like any market - are a parimutuel system. Your payout is determined not just by whether you're right or not, but by how many other people are also right. If you bet on social networks in 2004, you'd be right, but unless you're Mark Zuckerburg or Tom Anderson, you wouldn't have gotten rich off it.

So really, you need "a crazy idea that most people think is stupid, but is less crazy for customers than for competitors." Either that, or there has to be some barrier to entry that lets you execute but prevents everyone else from executing, even though they can see the same opportunity that you can.

Agreed, with one caveat: I don't define a successful startup as one that makes you wildly rich. (i.e. given Zuckerburg's "paper" value, I don't consider facebook as being successful... yet)

Yes, it's a critical ingredient for life in general.

Success is usually achieved by combining ability and boldness

I thought it was determination and luck.