In a typical merger, the parties will sign a confidentiality agreement. It's serious stuff. In fact, if a public company is involved, there are insider trading laws that are triggered.

Despite all this, there are often leaks. And, if they get some press, there's a good chance that the stock price will spike. Actually, a leak may mean that a deal falls apart.

Now, we have some academic validation. That is, Intralinks and London's Cass Business School conducted a study on 350,000 deals from 1994 to 2007. Among the deals that had leaks, only 49% closed. This compares to a 72% close rate for deals without leaks.

Why? I think there are several reasons. First of all, a leak will engender some distrust. Is the other side manipulating things?

What's more, a leak is likely to make a deal more expensive as traders and hedge funds jump into the stock.

Interesting enough, in light of the current environment -- where credit is constrained -- this may put even more pressure on potential deals.

Tom Taulli is the author of various books, including The Complete M&A Handbook and The Edgar Online Guide to Decoding Financial Statements. He also operates MergerBook.com.