I got the 33% success rate from here:
http://gamerant.com/kickstarter-video-game-failure-rate/Don't get me wrong, I am not on-the-barricades angry at Kickstarter or anything. I disagree with some of their policies, but I still think it's a great platform and I love how they help make a lot of awesome niche projects possible. It's just that I keep seeing these discussions about what crowdfunding is and what to expect. I think that is caused by stuff like passage I quoted and a lack of disclaimers. It would be nice if there was a bigger consensus on what to expect, and Kickstarter can and should do something about that.
Thinking about it, I was wrong to suggest they do better to screening. But they could do better disclaimers, and they could do a better job facilitating communication. Make a framework for financial transparency, give friendly reminders to developers who stop communicating, reach out and avoid stressed project creators hiding from backers, etc. They should help connect backers and creators. That's the vibe I get from their page, but I don't see any evidence they're actually doing much once a project is launched.
As for your last question, when I worked in the games industry, I did see games canned. There is a constant flow of prototypes and pitches at all major studios. Most of these get canned. Others get canned in the early phases, or transformed/merged into something completely different. Projects being canned after significant production has happened is a lot more rare. It's usually better for the publisher to eat a loss than to just write off the entire development. The result of a failed project tends to manifest as studios being shut down or downsized.