The key issue here is that lots of FLOSS projects only reach the 80% mark (and those are the really good ones) where the missing bits are the "boring bits" like polish and documentation.
The suggestion is that it would be good for the FLOSS community to motivate/enable developers to put more effort into those boring bits (true) and that funneling money with the right strings attached is probably the best way to do that (also probably true).
The next step in the chain of reasoning is that the best way to funnel that money is to enable FLOSS developers to sell something to one group of people while still being able to share most of that thing freely with another group of people. I think this is the link in the chain that many people really have a problem with, so they/we don't have any patience with the next link in the chain which is contributor agreements.
So I wonder if the conversation we need to be having is not so much about contributor agreements as about business models. Certainly some models have been found that channel some funding into FLOSS but it seems they aren't enough. In particular they don't seem to help with the "last 20%" problem. Is there a new business model?
The "app store" model has shown that you can make a lot of money by selling something for 99c to enough people. The "humble bundles" show that people are willing to pay for quality when given the opportunity.
I myself would be willing to drop a few dollars here and there from time to time to support FLOSS projects, but there doesn't seem to be any easy opportunity.
It feels like there should be a model that allows those who want to fund software to be "* supporters *" and there by enable developers to finish the job, but I have no idea what it is.... I'm sure it isn't a "--donate" option on all programs....