I'm a little late to the discussion, but I have to point out it's actually very easy (and free) to create your own "Wwwizer" on Heroku (this assuming that your DNS service cannot solve it). It's just 8 lines of code.
Shameless plug, but if you want instructions: http://bionicspirit.com/blog/2012/01/10/domains-merged.html
Alternately, use any competent DNS provider.
You can also do this with CloudFlare in front of your site and get all the other services for free as well.
I prefer naked domains. www., feels like a hard to pronounce anachronism.
Why in the hell would you want to do this?
Wow, this is a terrible idea. Pointing all your domains to a service you don't control with no formal, legal contract on what they can and can't do with the domains you point at them?