momentum can make poor decisions seem wise. Perhaps we remember the NASDAQ's high of 5048.62, during the height of the tech boom, and not when it fell to 1114.11 in 2002 when the tech bubble burst. But bull markets do not last forever, and it's important to make sure we 're evaluating companies based on their long-term value, regardless of market cycle. Of course, not all overvalued companies are bad companies. Twitter, for example, has a sizable user base, solid revenue growth and an undeniably disruptive and innovative technology. It's safe to say that Twitter has a lot of potential. However, the company's valuation is simply not justified by its fundamental performance. Twitter's stock is trading at nearly 45 times its 2013 revenue, and its profit multiple -LRB- a company's market value expressed in terms of its earnings -RRB- is nonexistent, given that it has yet to establish a profitable business model. Sure, there are some companies, like Amazon, that do n't meet traditional metrics of financial strength that end up performing incredibly well in the stock market. But they are the exception, not the rule. Consider the example of Vonage, one of the hottest IPOs of 2006. Despite losing 97 cents of every dollar in sales, the company had a $2.6 billion valuation. The company's fundamentals did not match its valuation. The results speak for themselves, with Vonage shares