This is an interesting topic. It came up on a newsgroup some time ago; I don't remember where. A pilot complained that he'd gone flying on a particular day, wx diverted into some place, and was charged the standard landing fee, even after this programme was put in place. He was expecting sympathy from other posters. He got absolutely slated. Why? Because on the day he chose to fly, the weather was forecast to be non-VMC and pretty much all over the country it actually was from morning to night. He was criticised for not exercising good airmanship in choosing to fly in the murk and then expecting a freebie when he got caught out.
On the face of it, free landing fees for a wx divert sound like a good idea, but in practice I'm not sure they accomplish anything and may even encourage poor judgement. If the weather's dodgy enough that you end up having to divert, unless it's a sudden and unexpected condition, why would you choose to make the flight in the first place? If you do decide to give it a go and see how it turns out (and, in this country's weather, who amoungst us hasn't done that?), you do that with the full knowledge that you may not get where you're going and you may not be able to get back. The consequences are well known before you start out and responsibility should be accepted for them. The release of the landing fee seems to go against the basic premise in aviation that the pilot is completely in charge and expected to act like, and accept the consequences, like a professional adult.
Now, a free diversion for an unexpected technical failure, that's a different story, and I think that idea has some legs.
Just my .02 worth
Pitts2112