Consulting Mag., Vol. 9, Jan./Feb. 2007 at 17, describes a lawsuit against PricewaterhouseCoopers, which case unearthed evidence that the accounting firm had obtained discounts from travel companies. That would have been fine, except PwC structured the discounts as backend rebates rather than front-end discounts, and pocketed the rebates.
Some large law firms might also be able to muscle in on similar kinds of savings from airline tickets or hotels, so law departments ought to confirm that they as clients obtain the benefits of those savings (See my post of June 15, 2005 about ethical obligations of law firms to pass along savings to clients.).