Ziff Communications Co., the nation's largest computing publishing company, went up for sale. The price tag: from $2 billion to $3 billion. The firm is selling all its publishing holdings, including PC Magazine, PC World, MacWorld, MacWeek and several electronic-information businesses. The New York--based company has annual revenues of over a billion dollars and growing. So why leave the business? It's speculated that the Ziff brothers, Daniel, Dirk and Robert, who now run the family's interests, wish to concentrate on other areas of business.To post your view, click Time Message Boards, open Science and Technology folder, select "Future Technology . . . Predict".