If queries are ever made using natural language and require no further user intervention, voice recognition and vocal output is worthy of imagining. Visualise a scenario where you ask a question and get a series of answers with level of certainty for each. If you are unsatisfied with the foremost (top-level) response, you may explore the other possibilities which have been perceived as reasonable by the knowledge engine. You can also explore laterally, forming your own opinion based on the facts which are available in the form of strongest citations.
Privacy become a major issue too. One must separate out names of individuals and businesses or have it tightly moderated, which is bad practice. Censorship by service providers over content is often harshly criticised, in particular Google's political censorship in China.