Why are so many CRM implementations still failing?

According to many market analysts, the market for CRM solutions shows no signs of slowing down. It’s increasingly rare to find established sales organisations of any significant size without some form of CRM solution.
And yet when I talk to many sales leaders about the current state of their CRM implementation, the most consistent impression is one of promise unfulfilled.
They frequently acknowledge that key success metrics around data quality, sales team adoption and impact on revenue still have a great deal of room for improvement.
Of all the possible influences on success, enthusiastic sales force adoption is probably the most critical. So why is it so hard to persuade sales people of CRM’s potential to improve their own personal performance?
The most obvious answer is that many of the traditional CRM platforms, and an even larger percentage of CRM implementations, are seen by their target users – the sales