I take my MBP almost everywhere i go. Just thinking to myself how convenient 3G internet would be to have when i dont have a wifi connection. I understand its not something everyone would want but could possibly be an upgrade for those who do.
I'd much rather use a Sprint or Verizon Mifi or USB broadband card and be able to use it with multiple machines than have things tied to a single machine.
I recently upgraded my USB broadband stick to a Mifi and will never go back. It's small (size of a thick credit card) and connect 5 machines at once.