[lazyasciiart]

The biggest issue I've seen is developers making business decisions knowingly, but without saying it to the business people. I was on a team that literally sat around saying "if we tell them it will take 18 months to do this then they'll just cancel it, but we want to do it, so let's say 6 months and then we'll just be late but they never cancel stuff in progress". I quit that team for many reasons, but they got started under that 6 month estimate and four years later the project is still going.