I've written endlessly in this column that your CRM data is far more valuable (and expensive to maintain) than the system in which it runs. The Hippocratic Oath for all CRM decision makers must be "above all, do no harm to the data." Even so, CRM systems must be maintained, extended, and integrated to meet competitive realities and business needs that evolve over time. And with each improvement to the CRM system comes implementation cost, changes in maintenance/operational costs, and risks to the data, so you have to consider the alternative of CRM system replacement.

1. Risk to Your Data

Sometimes, an existing system or its integration points cause data pollution: field corruption, record duplicates, or outright deletion. If this can't be resolved due to architectural or operational reasons, I can think of no more compelling reason to replace a CRM system.

2. Users Hate It

Since human interaction is the source for most all interesting CRM data, unhappy users undermine both the functionality and credibility of the system. In evaluating the user-happiness issue, you have to look way beyond the sales rep's UI: look at every external touch point that's feeding the CRM system. Do callers detest your IVR or your predictive dialer? Do customers get frustrated by your support web site? Does your e-commerce system have a ridiculous checkout sequence? If the central CRM system is an obstacle to fixing those problems, that's a pretty good argument for getting that system out of there.

3. Too Hard to Integrate or Extend

Most enterprise software has a very long design life. Not so with CRM. Too many marketplace issues change the rules—whether it's your channel, your competitors, or the customer standards of service. So it's almost inevitable that even the perfect CRM system will need to be extended or integrated in fundamental ways every couple of years. Don't believe me? Just wait for the request for Twitter marketplace integration. If your current system is too hard to integrate or too expensive to extend, it's only a matter of time before you'll have to move on.

4. Mobility and Extended Access

Users in many organizations are increasingly decentralized and mobile. In highly virtual organizations, they may be consultants, contractors, or partner employees. If your system doesn't have a flexible security model, doesn't support mobile laptops well, and can't be used on an iPhone, your field sales and support people are going to look increasingly weak vs the competition. This is not just a matter of flashy appearance. Mobile is the way people increasingly work.