Well if someone is looking to "grow" they're going to be stuck either way, unless they buy a full frame camera from the gate. Anyone who is buying a first Nikon DSLR be it a D40, 60, 90, 300 is going to be "wasting" money everytime they purchase a DX lens (in your theory), because once they upgrade to a full frame these DX lenses will bang out a crappy 5mp photo on your 21 mp sensor. So by your theory the only way to properly grow in a Nikon camera without wasting money is to throw down 3 g's for a D700 out the gate.
Not at all.
I don't recommend DX lenses, with the exception of the 55-200 VR which is dirt cheap. One can buy any of the full frame Nikon Lenses and use them with any DX camera... of course, with the D40/40x/60 (which wasn't introduced for quite a while after this post was orignally made).
What I have CONSISTENTLY recommended was that a person spend his/her money and resources on buying the finest quality glass and spend as little as possible to get the job done on the body.
I have never varied from that. I do not recommend DX lenses (again with that one exception) at all, nor do I regularly use any but the 18-55 VR (which came in a kit) and the 55-200. All of my other lenses, the 70-200 VR, 105 VR, 70-300 VR, etc. are full frame.
I have absolutely no intention of buying another DX lens, and only own the 2.
Nikon makes a LOT of good, relatively inexpensive FX glass, including the excellent and extremely cheap 70-300 G and the 50 1.8 G that people on a budget can pick up and use for years. Moving a bit up the line, the FANTASTIC 80-200 f/2.8 is well under one grand in the non-AF-S version. Pro level optics at a cheap price in that one as well. Or how about the excellent 60mm Macro 2.8 D? The sharp as a tack 50mm f/1.4 D? The blistering little 35mm f/2 D or the f/2.8 28mm D? All of these fantastic lenses, none of them will autofocus on the D40.
The lack of autofocusing with non-AF-S lenses was only one part of the article however. I find the 3 focus points a much bigger challenge personally with the D40.
I have a D40 and I use it a LOT. Most of the Hawaii pictures I have posted here over the last month or so have been taken with it, because it is light, cheap and if I drop it or trip when walking across a field of broken lava and it gets smashed I won't lose any sleep over it.
The little thing has fantastic image quality, that has NEVER been an issue.
Having said all that, I use the camera in strictly defined roles... where I want something light and cheap to carry around. Sooner or later it is going to die a horrible death, and I can live with that.
Any other camera in the Nikon system other than the D40/40x/60 can work fully with FX lenses... I can't imagine wanting to buy DX lenses for these cameras, so that kind of nips your argument in the bud.
Buy DX lenses if you like... I have no intention of doing it myself.
For starting out as a camera to build a system off of, I would rather have a D50 or a D70 (available used for the same money or less than a D40 now and at the time this was originally posted) than a D40.
Your milage may vary.