I think blanket permission (or some indication that permission will be granted, like the author already having said yes to podfic) will influence my decision on when I record something but not likely if I'll record and it's not a completely tangible thing. I think it's more like what you said in your post; I have a big list of things I'd like to podfic and if some of those authors have given blanket permission they'll move closer to the top of the list.
I think too, it depends on how I come across the blanket permission. I'm the one who runs the multipodicity Blanket Permission list, so I see a lot of authors on the list but I don't have any context for what it is they write (I'm horrible at names :S). If it's someone on my flist that might catch my notice more since I'm more likely to be familiar with them and their writing. I also run a shorter American Idol blanket permission list over at ai_podfic which, I have actually gone through and checked out some of the fic of authors I didn't know, just because they were on that list (since that's the fandom I'm currently reading in).
I think blanket permission is awesome but I also kind of wish it were presented better. A lot of authors only give permission in the comments on posts spread throughout fandom (like the ones I run, or the amplificathon and other comm specific permission posts). It would be so much better if they would post it to their journals, AO3 profiles, fic master posts, etc. Lists are great (as klb said, the list is a great place to send newbies), it's just, looking at a list of names isn't even the most useful thing. I have some plans that I'd like to put into motion to make the lists I run more easy to use and even just to spread awareness to authors so they know about this. But, I kind of have a huge list of to-do things for podfic so it might take me a while to put those thoughts into action. :P