There's a common conception in software that x% of projects never get finished... but to be honest, I'm not sure at all if it's the case - and it's hard to know because most projects that don't get finished, rarely get talked about.
So I pose the question to a bunch of other developers: How many projects have you worked on that tanked/didn't get finished?
EDIT> Maybe I should clarify; when I mean 'tanked' I mean, the project didn't get finished - as in, not functional according to the agreed upon spec (formal or informal spec).