Six days since the end of my project (tgf.fm/ks), 15 of my 1044 backers haven't gone through. I think a bunch have fixed credit card errors over the last week. Three of the nine biggest pledges had their cards declined, likely because of the giant charge to an unfamiliar vendor—but those folks have been in touch directly to resolve the issue.
Two out of 1044. Eight people also decreased their pledges after we hit our goal, which took me aback for a moment—before it made me retroactively extra grateful that people had given beyond their comfort zone just to help me cross the finish line.
I actually canceled a sizable ($1000) contribution early in a campaign. I got excited, pledged, and then talked to a buddy who actually has subject area knowledge in what the campaign was trying to do. He raised a bunch of good questions and I never got any good answers back from the campaign, so I didn't feel comfortable it wasn't vaporware and I withdrew the pledge. In retrospect, they were focused on the gee-whiz signed photo and coffee mug level prizes whereas I was interested in the actual end result hardware for science, and I think whomever was running the campaign just didn't communicate well.
I would feel very awkward waiting until the last minute and certainly if they were on the edge of the goal, but in that campaign's case I canceled in the first two weeks and they made their stretch goal anyway.
I'm a hardware engineer so I'm just incredibly suspicious when really cool hardware pitches can't answer follow-up questions with sufficient details. Lesson learned: I'm an impulse buyer so I'm not allowed to pledge money on Kickstarter without waiting twenty-four hours and talking to a subject matter expert.
