Current litecoin profitability:
1.2 million Khs of hashpower yields 28 litecoin a day
1.2 million KHS x .00001000 per Khs = 12 BTC
28 litecoin = about .211 BTC
ROI (without electricity cost): 56 days
ROI (with electricity cost): At least 110 days
Mathematically it is a Ponzi but as long as suckers keep putting more in then they can continue to pay out. With an over-abundance of stupid scrypt.cc has had a long shelf life.