The internet is exactly that. A collection of interconnected networks.
I’m a computer science student specializing in networking and low level programming. Essentially the Grid is just another network ON the internet. Yea, it has blazing fast speeds, and apparently amazing number crunching abilities… but there is nothing about it that keeps it from being simply another portion of the wider internet.

Realistically all that needs to happen to connect the two is simply plug an Ethernet cable into one of the nodes on the Grid. Yea, that’s a huge oversimplification, but it isn’t all that much more complicated than that. Assuming that the computers that this Grid runs on have anything resembling a TCP/IP stack (which comes on every operating system you could care to mention), and that the nodes on the Grid network have some kind of routing capability… your just looking at a giant LAN. Exactly like the one in your house with a linksys router… only spread out over half the Earth, and connected using incredibly expensive and fancy Ethernet cable (Fiber optic).

And I’m rather skeptical of the dynamic routing technology. It sounds exactly like circuit switching… the previously dominant routing technology. Circuit switching is what was used before the www she-bang. The problems with it were simply that once the resources were allocated you cant get them back until the user gives them back. So if you have a 40 minute phone conversation that has 30 minutes of dead air, you can’t recoup any of the lost 30 minutes. Packet switching was developed on the principal that the ISP’s only wanted to have to deliver what the user actually wanted delivered. With increased complexity and sophistication, I’m sure dynamic routing might be feasible. Perhaps not better than what we have, but workable.
In terms of known data, such as a DVD, I can see some serious benefits of it… But the cost to the carriers will increase in comparison to packet switching. Which I suppose would be where other commenters mentioned pay per usage billing fitting into the system.

And in any case, speeds can only increase to the speed of the lowest capacity link between the user and the data. If your trying to access a webpage from a server that is using a 56K modem, even if your using a cable modem, or satellite connection, I guarantee you that you will never get speeds higher than 56k from that server. The only way possible is if something cached the data somewhere in between.

To Ender:
I don’t know where your from, and I can only really speak from my own personal experiences.
Cloud Computing is a BAD thing.
This is the situation that I am in right now. I came home from my studies for a few weeks to visit my folks. I helped my dad take out the trash for pickup the next day. But stupid me I must have tossed my wallet in with the big wad of receipts that I was throughout out. I’m currently in Chicago, in the USA with my parents. I can get around easy enough. And even though I threw away my drivers license, its not a big deal to have unless I get stopped by a police officer. I’m a good driver, so thats unlikely. But, I went to the department of motor vehicles the other day to get it replaced, and they can’t help me. All of the papers that let the American government know that I’m a real person are sitting on my desk 200 miles away at my school.
Yea, they have policies in place to help out with this, it just takes time, but its not that big of a deal.

But imagine this.
Say you like to listen to the band Aerosmith. I like some of their stuff. Your computer uses the cloud for storing your music collection. What if Aerosmith, or whoever happens to own the copyright to their music, decides that they don’t want to let anyone listen to their Aerosmith music unless they give them more money? Given general complexity issues with data-storage, I shit you not it is way more cost effective to store only a single copy (or at least a few local caches of a single copy) of a single song, than it is to store every single version of compression, decompression, recompression, transcoding, and what have you of that same song.
So… stopping people from listening to the song that the copyright holders want to charge more money for.. well, that’s trivial. It’s as simple as flipping a bit on the machine. Access–. so on.
Whenever you allow someone else to control any aspect of your life, you are allowing them more power over you than you realize.
I can get my drivers license back, but only because the people I’ve spoken with are good people, and they understand my situation. They won’t get anything more or less in compensation for helping me out than they would if they told me to fuck off. I effectively don’t exist as far as my government is concerned. I have absolutely no way to prove I am who I say I am. Yea, my picture is all over their databases… but that isn’t proof. Thats just coincidence.
The people who happen to want more money for those songs? Well, they have a very very good reason to tell you to fuck off if you don’t pay their bribe. They want their bribe…
Or hell… what if the database just forgets who you are? Accidents happen sometimes.