The fact is marketing fluxuations are very common in this business. Although I disagree with some of what has been said in this thread.
Nikon did a horrible move a few years ago by adding encryption to the white balance data in their raw files. This angered some photographers who jumped ship to Canon. But every design decision a company makes like delaying a product or adding certain features or omitting others will influence some photographers who may suddenly take a dislike and leave.
Then there's the photographers who don't care enough about these minor problems. I did not like Nikons move a while back, but it was not enough for me to jump to canon especially since I had 3 Nikon lenses for my previous camera which would be compatible with my next purchase.
Finally there's the zealiots (sp?). They will buy their brand of camera regardless of how crap it is, and you see them arguing without actually saying anything noteworthy all the time at photography shops.
What I disagree with is the full frame or R&D arguement. Nikon doesn't stick to APS sensors because they lack the research to go full frame. It is simply a business decision, the APS sensors are easier to manufacture. Some photographers will sware green and blue that it makes a huge difference, whereas I know more photographers personally who use a Nikon D2X than a Canon 5D. Again this is the result of weighing up which features are important to which photographer.
In the end though the only thing that matters is the brand value. Nikon and Canon are considered the top 2 brands by those people who don't know any better, and by many who do. Pentax while making good cameras are less known, Sony is still considered "toys" by many pros, and something like this will not change any time soon.