* Wit Capital in New York has hired three executives. Susan Berkowitz, 34, joins the firm from theglobe. com in New York as senior vice president of marketing. Amy Cortese, 37, will serve as vice president and director of content after holding a similar position at BusinessWeek in New York. Bernie Siegel, 43, formerly of Waterhouse Investor Services, was named chief financial officer.
* Equitable Life Assurance Society of the United States in New York has named Stephen T. Burnthall, 46, senior vice president and Michael S. Martin, 52, executive vice president. Mr. Martin will remain as chief marketing officer and chairman and chief executive of EQ Financial Consultants Inc. , Equitable's broker-dealer unit.
* First Security Corp. in Salt Lake City has named James R. Beaudoin, 40, vice president of financial planning and estate planning in its private client group. Mr. Beaudoin had been with KPMG Peat Marwick in New York for 15 years.
* B. C. Ziegler & Co. , a brokerage in West Bend, Wis. , has promoted Bill Morse, 38, to senior vice president-national sales. He had been Eastern region vice president.
* Cole Taylor Bank in Wheeling, Ill. , has promoted Daniel L. Lueken, 50, to senior credit officer and group senior vice president. Most recen
