Given the wailing and gnashing of teeth this time last year [1] when Square raised $150M on a $6B valuation, it is entirely possible this is their last change to raise capital. If it doesn't work, and they can't cross the line into operationally cash flow positive they will become one of the larger unicorns to die this season. I really hope it isn't the case because I love their product and their service, but the S-1 doesn't paint a picture of hope. Doing some back of the envelope calculations I can't see any scale where they are profitable given their current fee structure.
[1] http://www.theverge.com/2014/10/6/6918211/square-funding-sin...