Nikon seems to target consumers who will buy MORE cameras - not necessarily more expensive cameras. They have advertised the D3000 & D5000 cameras, and then "tagged" the end of those ads with higher end products like the D90 or D300s - even the D700 & high end lenses. They do the same with their coolpix ads - tagging them with the P100, P7000, or SLR products.
Canon runs plenty of generic, broad appeal ads that mention powershot & Rebel models. But, they also run individual ads in higher end publications - like National Geographic - for their 5D MkII & high end lenses.
It's just a different way to look at the marketplace. But if you ask me, Nikon's strategy will help them gain more market share. And, as we all know, some D3000 & D3100 buyers will no doubt get the photo bug, and upgrade to higher end bodies & lenses in the future. And, if someone purchases a new digital SLR system now, chances are that they will stay loyal to their brand in the future.