On Wed, Dec 16, 2015 at 5:09 PM, Jeff Garzik <jgarzik@gmail.com> wrote:

SW presents a blended price and blended basket of two goods. You can interact with the Service through the blended price, but that does not erase the fact that the basket contains two separate from similar resources.

A different set of economic actors uses one resource, and/or both. There are explicit incentives to shift actors from solely using one resource to using both.

Illustration: If SW is deployed via soft fork, the count of nodes that validate witness data is significantly lower than the count of nodes that validate non-witness data. Soft forks are not trustless operation, they depend on miner trust, slowly eroding the trustless validation of older nodes over time.

Higher security in one data area versus another produces another economic value distinction between the two goods in the basket, and creates a "pay more for higher security in core block, pay less for lower security in witness" dynamic.

This economic distinction is not present if SW is deployed via hard fork.