The return one gets is a function of elapsed time since bitcoin started with every newcomer getting ever-diminishing returns even if they expend the (Moore's law inflation adjusted) same amount of work. With pyramid schemes, the wealth of those who got in early is entirely supported by those who came in under them at a later date. It's not entirely analogous as later bitcoin adopters aren't kicking back value to the early adopters, but there are similarities in the end result: someone new to bitcoin in the year 2029 has no chance of catching up with those who were new in 2009 due to the fact that the total number of bitcoins has been mathematically limited to 21,000,000: http://www.bitcoin.org/faq#How_are_new_Bitcoins_created