Facebook stock has been backsliding since the initial public offering last week, and now we may know why. It appears that less than 72 hours before the company went public CFO David Ebersman decided to increase the number of shares that would be offered by 25 percent after officials at Morgan Stanley assured the company that there would be plenty of demand. The stock was initially priced at $38 a share, but fell to $31 after trading on Tuesday. Still, in most respects, the IPO was a success, raising $16 billion for Facebook, which has been valued at $104 billion. Sources revealed Tuesday, however, that price slashing went on prior to the IPO, sparking regulator interest in the instance, which could face a more thorough federal probe.