If there's one area where Linux on laptops is lagging most, it's in its availability through major vendors. Big laptop manufacturers still seem to be hesitant to offer Linux as prominently as they do Microsoft Windows. Two factors are at play here: the size of the prospective market and potential user confusion.
Because the existing Linux desktop market share is small, Linux offerings from major notebook vendors still have a tentative, experimental air about them. The word "Linux" doesn't even appear on Dell's homepage, but go to Dell.com/Linux and you'll be redirected to a page where (as of this writing) you can pick one of four notebooks, all running "Ubuntu 8.04 with DVD playback" as the default OS.
Lenovo's notebook offerings only list "Genuine Windows" as the main option, and the company has scaled back Linux as a commercial offering, no longer offering Linux as a preinstalled item (at least in the United States). This isn't to say that Lenovo has abandoned Linux support and development -- just that to them, it isn't worth the effort to provide Linux in the same manner as Windows.
This doesn't mean Linux on brand-name notebooks is out of the question -- just that it's fallen to a bevy of smaller groups, commercial and un-, to accomplish the job and provide support. Canonical offers commercial support for Ubuntu Linux, of course, but it's also possible to go with dedicated and authorized resellers like Emperor Linux who provide brand-name notebooks with your choice of Linux distribution. Ditto Linux Certified, itself an Ubuntu partner.
What could cause this to change? Simply having Linux run well on notebooks isn't enough by itself; what's needed is more hands-on awareness. If people have more direct exposure to quality Linux installations via netbooks, phones, and many other potential target devices -- much as they have had exposure to Windows in many different settings -- Linux may come to be seen less as an exotic oddity and more as a consistently familiar choice.
Linux as a consumer-level OS has always been a difficult nut to crack, and that's gone for notebook computers as well as desktops.
What has changed recently, however, are the venues it can exercise its strengths in. The netbook market is set to expand and take Linux along for the ride (and, judging from the likes of Android, other forms of mobile computing, too). There's no guarantee that a strong showing in that space, however, will translate into increased growth elsewhere -- but it would be a mistake to count it out completely, and it might turn out to be a solid way to make that happen.