Some Wall Streeters are experiencing acrophobia. Others talk of vertigo. Whatever the buzz word, the feeling is the same: stock speculators have suddenly become woozy about the market's new heights. After a 230-point rise in 1988, the Dow Jones industrial average has zoomed more than 500 points this year, 200 just since the beginning of July. "I've been on this trading floor for 39 years, and I've never seen a market go up so fast for so long without a major break," said Donald Stone, a specialist in consumer stocks on the New York Stock Exchange.
Propelled by good economic news,...