On our retail footprint we block outbound traffic from customers with dynamic IPs towards port 25, our support tells them to use their ISP's port 587 server.... That being said, since all of our home users have 50 mbit/sec or greater upload speeds we are pretty paranoid about the amount of spam that could be originated.
We don't block anything on static assignments. Honestly, even as a very geeky user, I probably would not have noticed the block and I can confirm that it is massively important to lowering our spam footprint as a network.
I asked our support people, and none of them had ever really had an issue with this policy in terms of keeping customers. I agree with Ricky's current comment on this thread, blocking is unfortunately necessary on the modern consumer portions of the internet.
Exactly. Just like not having wide open SMTP relays became "unfortunately necessary" over a dozen years ago. It's just the way it is and there is a solution for it.