Should Twitter fans buy the stock?

If you're a Twitter fan who's interested in buying Twitter stock, do you know what you're getting?

Cramer can't help but wonder.

"I suspect individual investors think they're buying a great company at a fair price," Cramer said.

Unfortunately, that's probably not the case.

"At $42, what they're really getting is very good concept at a very expensive price," he explained.

The Mad Money host worries that Main Street investors who are buying now or who gobbled up shares of Twitter at the IPO are simply buying a piece of a company that makes a product they like.

But they're not doing research.

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Those who bought on the IPO, "didn't analyze the actual prospects of the company nor did they link the company's stock price to the prospects or they would have found it absurdly overvalued."

Although Cramer often advocates investing in companies that make products you use and like, he doesn't ever advocate the strategy blindly.

"You got to do your homework," Cramer said. "You've got to understand the company's growth trajectory, the profit potential, the long-term business model, the track record of the chief executive and more.

Had investors parsed through this kind of data, he thinks it's unlikely that individual investors would have held the stock as it surged 75% on its first day of trade.

Of course Cramer understands that some companies command unusually high premiums. However, in the case of , the premium is staggering.

At $42 Twitter has a market cap of $23 billion. According to published reports to support even a valuation of $8 billion, Twitter will need to grow its revenues at a compounded growth rate of nearly 30% per year for the next ten years.

There's also skepticism about some of the fundamentals including the business model, competitive position and staying power.

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Now, that's not to say can't go higher – they can. Momentum stocks sometimes defy conventional logic. That could be Twitter.

Nonetheless Cramer wants every investor who may be interested in owning Twitter to do homework.

"Again, it's a great concept," he said. "But that's no excuse for overpaying. Be forewarned about the valuation. Then, you can make a decision. You can get comfortable with the multiple or run in the other direction."

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