The hoopla continues over Facebook's initial public offering of stock, with word that the social media giant has increased the size of Friday's IPO by 25 percent.

According to a statement filed with the Securities and Exchange Commission earlier today, the company now plans to sell 421 million shares — up from the previous estimate of 337 million. According to Reuters , at 421 million Facebook's IPO would be the third largest in U.S. history, after those of Visa Inc. and General Motors.

Tuesday, as we reported , Facebook said it was responding to high demand for the shares with an increase in the expected price, to between $34 and $38 per share from the original estimate of $28 to $35.

If the shares sell at the high end of the new range, Facebook would raise about $16 billion.

As we've also reported, though, it's going to be next to impossible for small investors to get their hands on the stock at its initial offering price — and there's word that General Motors is going to stop advertising on the website because it questions the effectiveness of such ads.

Related posts from our friends at Planet Money:

-- Pizza Delicious Bought An Ad On Facebook. How'd They Do?

-- Is Facebook Worth $100 Billion?

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