Facebook listed in the US overnight, with predictions the company would raise $US18.4 billion ($NZ24.01 billion) in its initial public offering (IPO).
Facebook is selling an up to 18% stake in the company at a valuation of $US104 billion, comparable to the market worth of Amazon.com and exceeding that of Hewlett-Packard and Dell Inc combined.
The frenzied demand was expected to drive Facebook shares well above its IPO price of $US38 a share, which was already at the top end of its target of $US34 to $US38.
Mrs Van Leeuwen said the new rules prevented financial institutions placing market orders in the system until trading began.
"They have been only able to place limit orders, which is when the client must stipulate a particular price limit they would like to buy at. It will be interesting to see how this manages to control the hype and volatility on the day."
The new rule followed curbs and new trading requirements implemented by exchanges and regulators after the so-called "flash crash" on May 6, 2010, when the Dow Jones Industrial Averages index plunged 9.2% before recovering, she said.
In addition to introducing the circuit breakers - which paused trading in stocks and exchange-traded funds when prices moved 10% in five minutes - market makers must quit within a certain price range.
The Facebook IPO was likely to be the second-largest offering in the US behind Visa.
With advertising being an important factor for profits, it was interesting to see General Motors pulling its $US10 million of paid advertising from Facebook, Mrs Van Leeuwen said.
GM reasoned that advertising in the medium had proved ineffective for its business.
The closest comparison to post-listing performance for Facebook could be Google, which listed in 2004, she said.
The Google IPO listing price was $US85, but on listing the shares soared to $US100.
"With Facebook being such a well-known global brand, and there being a large anticipation around this IPO, it could be expected we will see a similar listing performance."
Another risk to the company analysts had noted was that founder Mark Zuckerberg (28) would remain the majority owner of Facebook.
"He is viewed by the investment community as a volatile leader of the company," she said.
Reuters reported Mr Zuckerberg would be worth around $20 billion after the IPO. Following the float, he will control about 56% of the company's voting shares.
For most retail investors in Facebook, which has more than 900 million users, the risk was getting trampled by institutional funds.
Financial advisers warned, if the stock soared, the average person might end up getting orders filled at a price much higher than they would have liked, and they faced the possibility of losses as the investment funds rolled in then backed out, taking the price off its highs.
Morningstar analyst Jim Krapfel said those warnings were falling on deaf ears.
"A lot of retail investors are not concerned about valuation. That's what is going to drive the first-day pop. I think anything over 50% [above the IPO share price] will be considered a successful offering. Anything under that would be underwhelming."
