There's a simple off switch for all online results in the dash, and it works. The dash is being improved so you can disable individual result sources, but that work wasn't ready in time for this release. I don't think there's any particular malice in the delay.
http://www.theregister.co.uk/2013/04/25/ubuntu_13_04_review/
Note to self: continue to expect the worst in people.
(Edit: no malice understood, just brooding...)