Have you contacted all of your customers in the last year?
Every company needs a function to stay in continuous contact with the existing customer base. Someone must know which customer sites are available for reference calls, the state of their implementation, and which features are in production use.
Does this sound like the sales channel’s responsibility? Most companies pay their sales force to generate sales but not to maintain the relationship after the contract is received. In some cases, companies have an account management function, but quota-driven sales people will focus on the 20% of customers that are likely to buy additional product. Or perhaps they rely on technical support to get the feel of the customer base from the calls they receive. But only 20% of dissatisfied customers call the vendor.
Most marketing departments take on the role of customer relations, since the relationship benefits the entire sales channel or channels as well as others in the company.