Things like this invariable involve artificially crippling a product in order to create a market segmentation that does not naturally exist. I have a hard time coming to terms with the virtue of this model.
Asking people for money before you'll give them the product creates market segmentation that does not naturally exist. There's no such thing as a "natural" pricing structure. I hope we can agree that, in pricing a product, your goal is to offer a fair exchange of value. Since different customers value things differently (for example, a billion-dollar business stands to gain a lot more from a 1% increase in revenue than I do), tiered pricing suits this goal more naturally than flat pricing.