David's 5th point is the most important, at least in my opinion. By Google running DNS, they can potentially collect your complete browsing behavior (since you'll go through their server all the time, not only when you search with them).
E.g., if they want to get to Dell's website, rather than typing "dell.com" into the URL field, they type "dell" or "dell computer" into the search box and then click on the first result.
So a reputable DNS service that did this automatically would be a direct threat to Google.
User A: Google DNS: search for dell, dns lookups; dell.com, chat1.us.dell.com, checkout.dell.com
User B: Non-Google DNS: search for dell
The point I'm making is, it doesn't matter if people use Google for DNS, because they're already handing Google more valuable information. But it does matter if they're handing it to OpenDNS.
Heh.
Right now, the privacy policy looks great on the surface. They are launching a new product.
But you can't deny that Google's entire DNA is to extract monetizable information from huge amount of seemlingly unrelated raw data.
That's why you have to take their privacy policy with a grain of salt.
Privacy Policy Changes
OpenDNS may change its Privacy Policy from time to time, and
in OpenDNS' sole discretion. OpenDNS encourages visitors to
frequently check this page for any changes to its Privacy Policy.
If changes are made, notice will be given in the OpenDNS sites
and the OpenDNS blog at http://blog.opendns.com/ and we *may* send
an email to registered using to notify them of the change. Your
continued use of our sites and services after any change in this
Privacy Policy will constitute your acceptance of such change.
Edit: emphasis in the quote was mine
It's getting to be a very rare (non-technical) user who actually types URLs directly into their browser; most people go through Google, even to get to sites where the domain name and site name are exactly the same. They're hitting Google for every single site they visit already.