"Cash flow positive" sounds pretty straight-forward to me (would you care to explain how it is not?); sure, it may not have been profitable over its entire lifespan (which is perhaps your definition?), but once your cash flow in a given period of time becomes positive, if it stays positive you'll make up for any historical loss eventually.
Cash flow: +$700m. (Positive cash flow.)
Net profit: -$500m.
Cash flow accounting comparisons are generally only an appropriate measure when expenses generally relate to the period in question OR when expenses stay the same from period to period. Both of those seem to be pretty questionable assumptions wrt a growing technology company.
Cash flows aren't exclusively tied to operational activities. You can lose tons of money on the operational side, but make up for it in investments and debt, thus making your company cash flow positive. I'm not saying that's the case with Facebook, but it's entirely possible that on the operational side they are losing money but still remaining cash flow positive.
The term "cash flow positive" generally refers to cash flow from operations. A company that closes a round of financing would end the year with more cash in the bank, but no one would call such a company "cash flow positive."
