This question directs us to look for answers in the wrong places.
First, it's looking for someone to blame. A blame culture never gets anything sorted. Second, it's offering either 'IT' or 'business' as the 'culprits'. This separation of 'IT' and 'business' is unhelpful as it's an old and increasingly inaccurate model - IT is a key part of the business in the vast majority of organisations, not something separate.
So (as much of the thread discussions illustrate) the question should be framed around what makes for successful projects and how can we learn from these success factors most effectively to ensure a significant increase in the number of such projects.
In my experience, business case, governance & accountability, process & methodology, architecture & design and project management are all crucial. But the single core success factor is adopting a collaborative project approach ie all those involved in the business case, design, build, commissioning and operation must participate as members of a single integrated project team with common shared team goals in addition to specific individual roles & goals - establishing & maintaining a "we're all in this together" approach, rather than as "us versus them" style that is bound to fail. Such an approach enables, in turn, the use of techniques such as joint rapid application development and prototyping that increase quality and decrease cost.