Facebook IPO Best and Worst Case Scenarios

Facebook released their numbers in preparation for an IPO, showing 2011 revenue of $3.7 Billion and profits of $1 Billion. Speculation is the IPO will be valued as high as $100 Billion.
This would be a P/E of 100. That’s high, but then P/E’s are not as significant an indicator for young companies with a lot of growth potential. So can Facebook grow enough to justify a $100 Billion price tag? I’m not so sure.
The easy justification goes like this:

Facebook has been focused on user growth and they were still growing 100% …