Failed projectsToo many projects fail. (Either are not implemented, or are implemented but are not well received, not usable, need major enhancement in order to be usable)
Not meeting business need
Many projects do not deliver what the business needs (although they may actually comply with the specification). Often the business need has changed over time and the specification becomes out of date.
Cost overrunMany projects cost more than planned, either due to overrunning the deadline (increased cost), due to adding people to catch up (increased cost), or by missing a business deadline (increased cost). Any of these circumstances may invalidate the original business case
People issuesDelivered solution may be unacceptable to those who actually use it (they generally haven’t been involved until deployment)
Poor management
Keeping to original plan, regardless of circumstances. Avoiding change (often seen as a bad thing, rather than a fact of life in current business circumstances)