good reasoning @voice-of-reason, however:

note that ISPs would not have to serve as miners. we are using the Steem blockchain model where ISPs would simply act as "service provider" similar to how Amazon hosts Steemit without being a "miner".

also, if Steem has value based on the content created on Steemit, the value of a token which powers all the content on the internet would be priceless!

then again do not forget, Blockchain is open, transparent, autonomous and decentralized. ISP cannot play unfair with a Blockchain powered system

finally, this is simply a concept, I am sure should the engineers sit down, they would be able to figure out a master plan to make it wrk!

we wrote a post exclusively to address your questions! read it here > https://steemit.com/savethenet/@blockrush/addressing-the-potential-challenges-of-a-blockchain-powered-internet-blockrush