Silicon Valley has a new case of "sudden wealth syndrome."

With more IPOs in the offing, from Zynga Inc. to Groupon Inc. to Facebook, the social-media craze has become America's latest supernova of wealth creation, launching a new generation of millionaires and recalling the instant riches of the 1990s dot-com explosion. Terms like sudden wealth syndrome and "affluenza," which had largely vanished from the offices of Palo Alto, Calif., and the cocktail parties of nearby Atherton, are back.

Yet when it comes to investing and spending their fortunes, Silicon Valley's newly rich are likely chart a different course from their predecessors. In the wake of the dot-com bust in 2001, which left many Internet millionaires with massive mortgages and worthless stock, the new tech magnates are likely to take a more cautious approach to their money. Advisers say the newbies are likely to sell as much of their holdings as possible and protect their cash.