Google has added three more names to its unofficial list of millionaire shareholders.

On Monday night, three executives at the search engine operator made filings at the

Securities and Exchange Commission

itemizing previously undisclosed holdings of Google securities.

The executives join the list of other Google executives and directors, including venture capitalists, whose holdings in Google have already been itemized in the company's IPO filings.

Though the price at which Google's shares will be sold to the public hasn't yet been set -- the company, in fact, plans to set the offering price by auction -- the interest surrounding Google's IPO indicates that the shares held by these insider shareholders will make a nice contribution to their personal wealth.

David Drummond, Google's general counsel and vice president of corporate development, holds 936,000 shares of Google's stock, according to his filings, plus options for an additional 66,500 shares. With outsiders calculating that Google has recently valued its own shares at around $90 apiece, that means that Drummond's holdings are valued in the neighborhood of $90 million.

Jonathan Rosenberg, vice president, product management, holds 850,000 shares and options, putting the worth of his holdings north of $76 million. Rosenberg joined Google in 2002.

Shona Brown, who last year became Google's director of business operations, has options to purchase 104,000 Google shares, at strike prices of either $9 or $26. Those options, which start to become exercisable in September, would clear $7.8 million for Brown were she to be able to exercise them and sell the shares for $90 apiece.

All of these holdings, however, pale in comparison with those of Google co-founders Larry Page and Sergey Brin. As previously disclosed in the company's IPO filings, each owns more than 38 million shares of Google stock, holdings worth more than $3.4 billion apiece at the $90 price.

What's unknown, however, is how many shares any of these insiders will sell -- if any -- when Google starts auctioning off its shares to the public. And as with any auction, it's unknown what the final price will be.

In its latest amended filing, Google reiterated and elaborated upon the risks it previously disclosed in related to the auction process.

"You should understand that the trading price of our Class A common stock could vary significantly from the initial public offering price," warned the company. "Therefore, we caution you not to submit a bid in the auction process for our offering unless you are interested in investing for the long term and are willing to take the risk that our stock price could decline significantly."

Even so, many observers believe the greater risk lies with Google's competitors, which range from

Yahoo!

(YHOO)

and

Microsoft

(MSFT) - Get Report

to

AskJeeves

(ASKJ)

and

Mamma.com

(MAMA)

.