"The IPO schedule worries me the most," Seymour said. "Because when companies are rushing, rushing to market to get as much stock and fixed income out the door, it tells you one, they're going to be using their stock as currencies and also that these are guys that obviously think this is a great time to get out."
Josh Brown of Ritholtz Wealth Management said that it was important to put the stock rally into context.
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"We're really just getting back to normal," he said. "I was much more comfortable being bullish when people hated stocks, and we're certainly not there, but there's a lot of room to make money in the in-between. People were positive on stocks throughout the entire '90s, for example."
StockMonster's Guy Adami said he didn't think the rally was in its final innings. Some great secular stocks could continue to do well, he said.
The one area that could be vulnerable to a bubble was biotechs, he said, adding that many investors haven't experienced a meltdown in that sector.
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"That concerns me," Adami said.
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Karen Finerman of Metropolitan Capital Advisors said valuations in "go-go names," such as Tesla, Facebook and Amazon.com had been stretched for a while—and now was no different.
"For us, though, I have no faith in my ability to call a market bottom or top, so when we go into a position we very often have levels at which we'd get out," she said. "And I try to sort of ignore what the market's doing and just stick to those as long as the thesis is intact."
—By CNBC's Bruno J. Navarro. Follow him on Twitter @Bruno_J_Navarro.
Trader disclosure: On Nov. 11, 2013, the following stocks and commodities mentioned or intended to be mentioned on CNBC's "Fast Money" were owned by the "Fast Money" traders: Tim Seymour is long BAC, SBUX; Guy Adami is long C, GS, INTC, MSFT, AGU, NUE, BTU; Guy Adami's wife, Linda Snow, works at Merck; Karen Finerman is long BAC, C, JPM, GOOG, KSS, SPY, MDY and short calls M; Josh Brown is long AAPL, GOOG, DDD.