I still don't agree because: (1) Consumers won't understand why they should make a capital investment and it will be a hard sell -- witness the trouble TiVo has had getting going. (2) Consumers hate installing anything. (3) A service is more efficient -- it can offer you a terrabyte of storage but no one will use it all. (4) A service can constantly update itself with new software. (5) If the storage sits in the cloud, you can play your stuff on any device in the home -- or anywhere else -- without having to network anything; if you store your stuff on a home-based server in the den, it's not going to be easy to get to yourself from the bedroom TV. (6) It's possible -- possible -- that an in-the-cloud service can deal better with copyright issues. That is, you can store a legal copy of (or link to) a show or song among your stuff in the cloud and play it anytime anywhere and copy it onto limited devices (a la iPod) but not endlessly duplicate and distribute it.
Jeff makes a number of good points advocating the service over the personal server. I have no doubt that today the service is a better opportunity, and that there are a number of constraints such as what Jeff outlines above. However, in response to his points I believe that technology will continue to change rapidly, prices will continue to drive down, and ease of use will constantly improve (plug and play all-in-one devices will become a reality in a couple of years-just look at the growth of wifi in the home as an example of how fast a new technology can spread). As for the practicality of an in-home all-in-one device, having an IP address for your personal server would allow you to get it from anywhere including your bedroom TV (no different from getting it from the Internet, especially if your home network has a faster connection). So it is not an either or proposition-the personal server idea will take time but it will happen in the next couple of years and be yet another viable option for the consumer. As for what opportunity is bigger, sure the service side will be, but that does not mean a service and personal server are mutually exclusive business models. Why couldn't Comcast give away Mirra personal servers, charge consumers a monthly fee, and have a cloud-based backup in addition to the backup on the home personal server. In my mind, that is probably how this will all evolve.
UPDATE: The personal server space is heating up in real time. Along those lines, Linksys today announced a deal with Maxtor to launch a wireless hard drive for easy network sharing with features similar to the Mirra personal server. While Mirra is a nice product, it will be hard to compete with the Linksys brand and distribution channel.