I agree with all of those who can see a definite market for this. I am a graphic artist and programmer. When I get home from my day job programming, I like to do graphic work, but prefer to unwind on the couch to do it as I have been sitting at a desk all day long.
My laptop is always plugged in. Basically, the battery is there so I can put the thing in standby and make it to my next location.
I also used to use a Dell XPS 17" monster for a previous job. I would work all day on it, then close it up, jump on the bus and the hour battery life was just enough to make my bus ride home (same thing on the way to work also), then back to the wall plug I go. So not only have I done an extra 2 hours of work on the way to and from home, I also now have all of my stuff with me, opened up, ready to go, exactly where I left it. How can you not agree that this is much more useful than leaving all your stuff on a desktop somewhere eg. at the office, and then transferring all the little bits and pieces that you need to take with you, every day. Trust me, it gets tedious. And then add on top of that the time and hassle of syncing all that data back up again. I lose productivity from not being able to take my work with me.
Before someone points out removable storage/portable HDD's, quite often in programming/graphic work, you cannot work permanantly from one of those. Plus I can stare at it on the bus all I want, but that doesn't seem to get my work done.
If I were to use a less powerful, lighter, less battery hungry machine, I would have lost days maybe weeks of productivity due to slower load times and much slower programming compilation times, especially as, being a programmer, I have a million tools open all at once. This is exactly the same as working in a graphic art capacity, probably much more so. And for what benefit? So I can sit for hours watching a movie without being plugged in? I'll get a cheap netbook too for that if I ever feel inclined to waste time. Seriously, I have rarely ever felt hampered by a short battery life, but I have all too often felt the pinch of poor performance.
As far as too much storage goes, I remember once coming home with a ridiculously expensive 40gb HDD (back when 10gb was the sweet spot) and saying that it would last me for ages. How could I possibly use '40 whole gigs of creamy goodness' (unfortunately, those were my exact words). 3 months later it was full and I was burning CD after CD of stuff, which just ended up getting lost, probably down the back of the couch. I now agree that there will never be a point when I have enough storage space. The only issue is, when it crashes, where do I put it all and how long will that take to do? But that is a problem for the future, as by that time, the recovered data will hopefully take up less than a 10th of the drive that is available at the time.
I will be hesitant to ever buy a powerful desktop again because the mobility productivity benefits far outweigh the slight power increase in being stuck at a desk. And forget lugging a 10 tonne lump of metal around. It is, in almost all cases, unpractical.