I was recently talking with a B2B Marketing leader who made the comment to me that “We don’t have enough customer references and case studies from our customers, including major accounts”.   I found that interesting, because this company is very successful and has great products and services.   When I asked why he felt that way, he responded that “we just don’t have good relationships with executives where they are willing to contribute to writing white papers, being interviewed for a case study, or offering to provide a positive reference, let alone accelerating sales and retaining customers.  My final question was: “How do you engage with them to build a relationship?” – and his answer was:  the sales team meets with our customer executives at least annually, and sometimes our executives will meet or talk with our major accounts, but we don’t feel like we know them well enough to ask. 
Interesting…  Here’s a thought.  Build out a programmatic approach to driving customer loyalty at the account level.  Can you say Customer Loyalty Program?.  Start with a one-on-one environment like a major account program targeted at your strategic accounts, but elevate the program to include your executives from product, sales, marketing, and strategy.   That will help you to engage at the right level in your strategic accounts, and move interactions with them from selling approaches to business level discussions.  Understanding the value you've already delivered, and the business challenges strategic accounts have will not only grow sales, but also put you in position to gain more references, case studies and white papers.