I love this idea!
MLM is one of the most powerful advertising mechanisms I'm aware of, and inspires a truly explosive grassroots phenomenon . Given that we are decentralized with no real official marketing/advertising, it makes perfect sense to take advantage of something like this. Its a natural fit for a decentralized system.
All MLM's deal with being called ponzi/pyramid schemes of course, but it is rarely true. So long as there is a quality product, no one is force to participate in order to use the system, and affiliate income is not solely based on new signups, we have nothing to worry about. Even with just 1 referral, if they make 4k transactions(at $.01 ea.) over 20 years, you've recouped your upgrade fee. You would only upgrade if you feel you can meet that.
So long as there is 1 person you know, not using bitshares, it may be worth the $20 for 20 years of tx fee's. If everyone within your reach already has an account, then obviously you can weigh this fact to help decide whether to upgrade.
conceivably every single person who upgrades can make more than it cost over 20 years. Even if every person on the planet already has an account, people are born every day who do not. And over 20 years need only make 4k transactions or less if they also upgrade.
My math may be a little off of course, and I havn't done any actual population growth sustainability analysis. but this looks very appealing. At that level of adoption it wouldn't matter anyways.
This is definitely not a ponzi, but I guarantee it will be called one. It would be good to have some solid rebuttals for this but ultimately won't matter. This will grow the system with or without the ponzi stigma. You shouldn't be afraid of that.