From Randy's Milemaster column-

"This is a story about upgrades. In fact, I can just hear Delta SkyMiles calling me now and saying, "I told you so." The Northwest WorldPerks program is just now making this announcement: Effective May 1, 2000, WorldPerks upgrades on domestic Northwest flights will be capacity controlled when upgrading from discounted Coach Class fares. This affects both complimentary Elite upgrades and upgrade awards using your WorldPerks miles. What does this mean? Well, I view it as a sign that the entire frequent flyer program industry is getting their upgrade programs taken to lunch by the increasing demand of upgrade benefits by its members, including the impact that these new alliances are having on elite levels."

See www.biztravel.com for complete story.