I cant see the problem with carriers not subsidizing the N900.
I always buy unlocked phones and use them with my Vodafone SIM which is on contract. Because I don't take a new phone when I renew my contract the give me a discount on my monthly package cost instead, so I don't really loose out. Just because you will end up buying the N900 direct from Nokia or via an Electronic hardware/Computer supplier rather than the network carriers shop means little too me.
I think this just reflects where Nokia are pitching this device. They say its more like a computer with telephony rather that a phone with computing. I don't expect a subsidy when I buy a computer.
Now this may not appeal to the general public and limit its sales as a whole but I vote for freedom to do what I like with a device and negotiate my network contact separately.