The purpose of any phone screen I've done is that it's simple enough that no self respecting programmer would have trouble with the questions, ie they are of the fizzbuzz variety.
The point being that if you need to "phone a friend" then you've probably already failed the interview.
How many positions would you estimate (I'm an academic so have no experience) where encyclopedic and gap-less knowledge is required to accomplish a task? I envision a technical interview as an opportunity to make sure the candidate can actually do the task you need them to - the screening of non-programmers should be done beforehand.
Ahh I see where we disagree, I might have read the blog post wrong. To me a phone interview is the actual screen. I'd never do an actual interview over the phone that was the basis for the final hire/no hire.
If the OP means phone interview as the actual interview rather than a phone screen then yes, I'd certainly relax my position somewhat.
usually for phone screens I'll open a shared google doc site and get the user to do a problem like fizz buzz.