More and more people I know are using portables as their primary or only computers. Some of them are buying the big "desktop replacements" behemoth laptops with 17 or 18 inch screens, a boatload of RAM, big (for a laptop) hard drives and expensive amenities such as Blu-ray players. Several 18 inchers were released last year just before Christmas:

However, it seems that maybe there's a natural limit when it comes to the size people will buy when it comes to a computer that they're going to carry around with them. None of the major vendors has gone up to 19 inches yet. HP and Sony each offer one laptop model in the 18 inch size, whereas the largest on Dell's web site is 17 inches. Note that Dell did, however, release a massive 20 inch laptop a few years back, which came with its own built-in handle.

Although the Dell M2010 was impressive looking, at over 18 lbs. it was just too hefty for most people to lug around. You won't find it for sale on the Dell site today, and although I did get a chance to see it \"in person\" at a Consumer Electronics Show (CES), I never knew anyone who actually bought one. Maybe it was the weight - or maybe it was the $3500 base price. Or maybe it was a combination of the two. We also heard that the battery life was understandably shabby - around two hours at best. There comes a point, after all, when bigger is no longer better; it's simply bigger.

A desktop replacement makes sense if a laptop is going to be your only computer, but it seems quite a few folks are getting by these days with a lot less. The hottest selling segment of the PC market is still in netbooks - tiny machines with skimpy specs that sell at low prices. And for someone whose only need for a computer is to check email, surf the web and create a word processing document now and then, a netbook may very well suffice.

On the other hand, for about the same price ($350-400) you pay for a netbook that has 1 GB of RAM, a 120-160 GB hard drive and a 1.6 GHz Atom processor, you can get a desktop computer with 4 GB of RAM, a 320 GB hard drive and a 2.3 GHz AMD processor (specifically, I compared an Acer Aspire One 751h and an HP p6100z; both were advertised for $349.99).

I know which one I'd buy if it were going to be my only computer - but then, I want a full-fledged computer. A recent study showed that many people who buy netbooks are dissatisfied with their purchases afterward - and that the biggest reason is that they were expecting the performance and functionality of a normal computer.

http://www.osnews.com/story/21711/Study_Says_People_Dissatisfied_with_Netbooks

Whereas a desktop system will probably always give you more bang for the buck, it's not easy to pack up a tower (or even a mini tower) and monitor and take it on the road when you travel, although it's not impossible, either. My son recently took his Core i7 desktop with him to a chess tournament in St. Louis, but he was driving. It gets more complicated if you have to fly. This week he's in Spain for another tournament, and he has his laptop with him instead.

Just how important is portability, anyway? One could make the argument that it's actually less important to take a portable computer with you everywhere today than it was a few years ago, because so many of us have smart phones with data plans, which can perform many of the functions of a computer and fit in a pocket. If all you need to do is read email and surf the web, you can do that with a Windows Mobile phone like my Samsung Omnia, an iPhone, a Palm Pre, or one of several other high end phones running sophisticated smart phone operating systems.

In fact, my dream device is a handheld computer/cell phone the size of the Omnia/iPhone, with complete USB functionality (i.e. the ability to plug in a USB hub and attach a keyboard and mouse, even a USB hard drive) and a video out port to output to a regular monitor. And if someone would market small (12 inch or so) flat panel monitors with stands that fold down so you could easily slip them into carrying cases and take them with you, you wouldn't need a laptop/netbook for traveling at all.

Of course, most of us wouldn't want to have a phone as our only computer. But since we wouldn't need to buy a laptop or netbook, we could spend that money on a real (desktop) computer with much more powerful specs instead. If this scenario came to pass, I think desktop sales would start going up again, and the market share of portable computers (other than smart phones) would decline.