But as KristiF08 commented: "Those of us in industry marketing are pretty familiar with these reasons 'why not.' What I'd really like to know is how to influence my project managers and consultants to work with a client throughout an engagement to get the client to change their mind. Industry media aren't interested in unnamed case studies. Can someone offer some tips as to how to influence the client relationship so they see the value in participating in a named case study/press release? I've yet to find them."
One of the practices that's really common out there, of course, is cutting sweetheart deals for customers who are willing to sing your praises. It seems like a sort of sleazy practice to give a customer the financial incentive to speak on your behalf (i.e., how truly genuine, therefore, is their testimonial?) ... but that is a VERY common way that vendors entice their customers to talk. The trade bait might be a lower price on the service / product, or additional services beyond what's being paid for, etc.
Another common way to entice customer participation is to appeal to the ego of someone who works there. I've primarily done PR in high tech, and it's quite common to find an enterprise architect or similar who is interested in making a name for his/herself. The IT infrastructure is core to the customer's business, and here's a person who wants to be viewed at the cutting edge of technology (and continuously ushering in new approaches that increase their company's competitive advantage). If you can get this type of individual in front of industry press, it gives them further access to personal recognition. If people feel like you're asking them to whore out your product, that's not terribly enticing. But if people feel like you're giving them a platform (i.e., media opportunities) to discuss their roadmap or vision, they become much more receptive to participation (and your product invariably gets that positive endorsement you were looking for anyway).
As far as more specifically getting buy-in on case studies / press releases, one huge advantage that I've discovered is writing them BEFORE asking for permission. When you ask for permission at the onset, the customer's imagination runs wild and their guard goes up. They envision this really painful series of events around helping create this collateral, getting it approved, etc. But if you take the initiative from day one to capture the content and chronicle the customer's experiences / benefits of using your product or service, and then present a draft write up to them for review -- it becomes much easier to get buy-in. Make it very clear to them that you won't publish anything without their express consent, and that you will strike anything they feel uncomfortable with. Taking that initiative to create the collateral and THEN show it to them somehow gets you past a lot of the typical reservations that they might have had. And (it might be sort of manipulative), but they typically recognize the work that went into it and somehow feel a little more compelling to just go along with it.
The style of the writing in the case study / press release can also be a huge factor in whether the customer ultimately goes along. Often what I see are these super breathless / exuberant types of write-ups (by the vendor) where they've got the customer giving excessive praise to the product. You're much better off being relatively objective and subtle (and portraying the usage / adoption in an honest light). Sometimes the rhetoric can be so over the top that the thought of having their name associated with it really turns off the customer.
And there's something very reassuring to customers about knowing where the content will ultimately end up. It's good to point out similar case studies that have been done by your company (to show them that you can be trusted to pull it off in good taste, and that others have gone through your case study gauntlet and still have all their limbs intact).
Btw: Jennifer Alsever wrote a great piece on "How to Get Your Customers to Solve Problems for You" for BNET recently. I think the third section of that article ("Make Engaged Customers Feel Special") has some points that are really material to this challenge of getting customers reference-able.
Image from Tiggywinkle's photostream on flickr creative commons.