About Magicdice: The longer you play the more likely you will lose your Steem. It's gambling, so the bank always wins. I don't know wether "investing" in gambling has ever been a good strategy...
About Drugwars: like many others said, it's like a ponzi scheme. The users will only get 80 % of the amount they pay in. In the beginning it did make sense to invest, but only to a certain point.
I think there would have been even better ways to invest your Steem than into gambling and ponzi schemes ;-)