In the past I've opted for more expensive pledges to get "involved" more in the project (e.g. access to forums during development) and have NEVER ONCE actually taken advantage of the extra access.
I still have some projects, though, that promised delivery in 2013 that haven't delivered and haven't been great about updates.
The second project I backed that was controversial even though it delivered what was promised was CLANG. I still think it had the best promotional video I've seen for a Kickstarter project.
But importantly: they delivered what they said they would for the $150 I gave them. They just weren't able to get funding to take it to the next level.
The first project that was controversial even though it delivered what was promised was Oculus Rift. As I've said elsewhere, "Backing the Oculus Rift Kickstarter project at the $300 level (like I did) makes you a pre-paying customer NOT an investor." So I disagree with those people that somehow felt they were owed a piece of what Facebook paid for Oculus.
That "law" probably isn't as true with big teams, but for individuals or small teams with much more work than they expected, it seems very common.
One thing is clear and maybe this should be somebody's law: the more a kickstarter project exceeds its goal, the later reward delivery becomes.
I've backed around 25 projects on Kickstart to varying degrees of success.
Only two actually failed to hit their fundraising target. A few delivered exactly what they promised (although not always without controversy as I'll get to) but many are still (in theory) going a year or two after they were supposed to deliver.