Many early CRM implementations were justified on the basis of sales. The theory goes, the more you know about a customer, the more you can sell to them.
While widespread, this approach was/is probably most evident in banks; with hundreds of thousands of customers, stacks of detailed financial information about them and potentially hundreds of products to sell to them, an improvement of 10 percent would have a big effect on the bottom line. With the "cost of acquisition" of a new credit card customer put at more then $200, adding new customers from existing mortgage and savings customers would represent massive savings.
Unfortunately, this "we sell stuff to you" approach - with its emphasis on cross-sell and up-sell - blinded many companies to the service and value-add benefits they could achieve by thinking from a customer's perspective. If they'd done CRM properly, I would be able to access all of my accounts from one internet banking service without needing to fill in more forms. I wouldn't need to keep telling them my address on every form I fill out for loans or new accounts. And most of all, I could ring credit cards and they'd know where a dispute was up to without having to transfer me from call centre to call centre (where they insist on getting my full name and address every time for "my security" - read "their laziness").
The key question to ask in your business isn't what extra stuff can you sell to customers, but what better value and service can you deliver selling them the stuff you already do. If they like you, they'll want to buy more stuff.