The same, tired "I don't need it so no one does!" argument. I can't see myself ever using a dildo, but there sure as hell is a market for dildos.
Ditto for netbooks - they're selling like hot cakes... You might not be that mobile and can't see yourself in a situation that requires a small, honestly junkable, simple device for checking email on the go - add up to 8 hours of battery life on the new breed and it makes complete sense to have one if you're a student, traveler, or just mobile.
I have a macbook pro (2008 model) that costs more than 8 netbooks.. I don't want that to get stolen, so I bring out my MSI Wind.. I've had it for 2 years and couldn't care less if someone steals it from my messenger bag - it cost $300 and I've gotten enough use out of it to not care if something happens to it.. Sure, there are $500 laptops out there but they tend to have sub-2 hour battery life and are way to big to just have by your side in a shoulder bag. During my x-mas trip I used my netbook to check email, watch xvids, charge my phone while away from a plug, and kill time while waiting for flights.