"TheGlobe.com came public, went up 600 percent on its first day. Egghead.com, which was a software retailer, switched from bricks and mortar to an online firm, ultimately disappeared," he said. "A Wall Street Journal reporter had told me years ago that his grandmother bought it because she liked the name and actually made money on it. There's no public participation. That's really the hallmark of a bubble. That's noticeably absent today."
Shares of Facebook, which beat Wall Street quarterly earnings expectations, trades at 36 times its forward price-to-earnings ratio.
Insana noted that the metric was a far cry from that of 1999.
"There is a notable difference in terms of multiples and also in terms of when you look at revenue and profit—they exist in the companies that are going public today," he said. "If you go back to '95 through 2000, there were companies that came public with no revenue, no profits. They used the proceeds of their IPO to launch massive advertising campaigns before they had a completed product or service. In that regard, this is a vastly different environment. That was all promise, no fact. This is at least some revenue, some profit. Even if you look at a Facebook or Twitter, there's money there."
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Herb Greenberg, editor of Herb Greenberg's Reality Check, questioned whether investors today heeded the lessons of yesteryear.
"We repeat it, but have we learned? And I always believe, you know, we're in a new cycle, they're new participants, they weren't there, and they always think they're smarter than everybody back then really was," he said.
Greenberg noted that online retail giant Amazon.com's revenue—$81.76 billion in its year ended on June 30—is substantial.
"When it comes to Amazon, you could argue that if they really wanted to not make it work, that is stop reinvesting in the business, stop making the customer experience so great, that really the model could be questionable because the minute they stop investing in the things that make it so great, they can make some money and they can look good," he said.
Rosecliff Capital's Mike Murphy said that Amazon then and now resembled two different companies.
"You can't knock the revenues that that company's generating. And look at the price-to-earnings multiple today versus 1999. You can't compare them," he said. "There's a much better valuation argument to be made for Amazon today than there was back then."
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Josh Brown of Ritholtz Wealth Management said that the 1999 tech bubble even affected "real companies with real business models."
For instance, Cisco was once worth $600 billion, or $25 million per employee, Brown said.
"So, it was a real company, but we were still willing to pay almost anything for any stock, so long as we thought someone would come along later and do the same," he said.
"The top 50 stocks in 1999 had gone up 100 percent that year and sold at a multiple of 100 times earnings. Right now, our best 50 stocks are up an average of 30 percent in the last year, and they sell at roughly 21 times earnings. It's night and day."
—By CNBC's Bruno J. Navarro