The theoretical benefit of implementing SPF without enforcing it is that we build a situation where we will in the future have something enforceable which will provide practical benefit.

If it is a standard that everyone else has adopted, then the non adopters will fall into line.

Its really simple, all my domains are corporate domains. I can check the logs very easily and determine which other corporates they email, or they can tell me, and if I quickly see that they all have adopted SPF, I'll know its safe to act on the info and any new corporate looking to mail my customers will have to implement SPF in order to do business with them.

However, if all my customers contacts are sitting waiting to see what everyone else does before acting, then nobody will act without the introduction of an email governing body, which is what we'll end up with if we won't act without someone there to kick our ass and whip us into line so that they can take responsibility for killing the spam problems and charge us a tax for doing it.

Really, you have a simple thing to set up, set it up, it'll cost you nothing to do it and you'll enable an ungoverned sector solve its own issues and remain ungoverned. However, fail to act, and you will be supporting the introduction of a governing body who will in all probability implement the same solution and charge you taxes for enforcing it quoting the reduction in the cost to businesses as being a huge saving they've achieved.

Bottom line is that it is simple and easy to setup SPF, costs virtually nothing, do it, and who knows, maybe no benefit will come from it at all, but not because you sat around talking about it instead of implementing it.