Don't get me wrong - I'm not implying that the learner now knows as much as the teacher. Please note, I have refrained from equating information with knowledge. Effective teachers breathe life into information and convert it into knowledge. I'm merely pointing out that learners can instantly access information (assuming they have sharpened their search techniques) that had been within the firm domain of the instructor. This prompts teachers to maintain a conscientious command of facts since learners can quickly fact-check for accuracy. It should also serve as a reason for teachers to move well beyond rote facts and low level comprehension exercises and promote higher order thinking skills.
Here's a relevant excerpt from best selling author Daniel H. Pink's book, To Sell is Human.