I've seen many projects crash and burn at a digital agency. Including large ones where much money and reputations were on the line. Though I have not been part of a startup Company whose primary product failed.

What are your experiences with it?

It sucks. Tensions run high, people carefully determine the cause of the failure while assigning blame in different directions yet trying not to be offensive.

Could it have been prevented?

In my case, absolutely. A lot problems [including my own] were the result of being overconfident in ones ability to build a large feature in one huge sprint / development pass. Bugs slowly stack up but are dismissed early on, requirements begin changing, it turns out you badly misunderstood the scope of the project. Now half the timeline is gone and every meeting the heat is turning up, until it's become clear the deadline will be missed and the client won't be happy.

Can the same mistake be prevented in the future?

Most of the time yes. But it's usually not that simple. A decent team will try very hard to cover all their bases when planning the project. Nobody goes into a project thinking they overlooked a preventable mistake. But understanding the scope of the project's requirements and desired timeline is usually a big factor. Having developers who think critically about the state of development and where it sits in the context of the project timeline and client expectations is also important. But really a project can fail at any level on the team.

Do projects be destined to fail over and over again?

In some cases at the digital agency I worked at, the answer was yes. There were too many people in the process, all representing they're knowledgable in their respective fields, all with different assertions and expectations. Budgets would get blown too early as the project moved through different silos in the agency (planning, ux design, graphic design, copywriting, media/seo/social). When the project would be ready for the developers to start their work, many times they'd be under pressure and tight deadlines because the budget was already burnt up.

What saves a project?

That's a tough one. People will to stick they're heads out of the weeds when they see potential problems. Even if it might not be their specialty or possibly spread judgement onto other parts of the team. People who are diplomatic about this, and not everyone can do that. Some people just go heads down and rogue, and don't really care about the big picture.

Having a smart team who trusts eachother and watches eachothers back is huge, but that still won't prevent all forces of failure. Clients can certainly throw a wrench in the project too, by changing requirements or setting unrealistic expectations on their vendors.

The one that gets me is:

"I want this crazy idea, is it possible?"

"Well it's kind of possible, but, it's really not a good idea because <insert very good reason that is completely ignored as only "it's possible" was heard>."

"Do it for me."

To avoid this repeated mistake, I've just had to get better at saying "No, because it is stupid, will fail and is a waste of my time." This is easier as a contractor because you say you will walk, and can do. If you don't take a long contract all you have to do is not renew. They have to listen if they want you.