A pyramid scheme built in sounds interesting... so Bitcoins pyramid block rewards (half the bitcoins block are worth 50 BTC, then half of that worth 25 BTC, then half of that worth 12.5BTC and on and on) aren't a pyramid but I guess having account fees go to every MicroCash user is a pyramid.....
MicroCash is a pyramid scheme because it steals from the poor to give to the rich. Bitcoin doesn't steal from anyone, and the block rewards are payed from a fixed and limited supply to those who take the time and effort to secure the network. It is not a pyramid scheme.