Before an IPO, if investors ask for more shares than available, who gets how many shares and on which criteria?
A broker will only get so many shares for any IPO. They will give their highest profit customers priority, but try to keep the smaller ones happy as well. So where my TWTR order today was for 1000 shares, I actually was granted 100.
In the dotcon* bubble of the late 90's, there were some stocks I saw as many as 1000 hit my account.
(*not a typo, this is the title of a book on that period, the making of a bubble and irrational doings on Wall Street.