Learning how to do advanced searches is useful. Also learning which are reliable sources and which to avoid.
Google scholar is quite nice to use and you can also look at how google data mines and produces adverts specific to you and comparing google chrome with Tor if you want to be anonymous rather than using 'private browsing'. How anything put online is there forever so you might think the pic of you at a party with doggy ears on is funny but will it still be funny when you are looking for a job.
Why does everyone (almost) use google as a search engine? What are they alternatives? What is the difference between a search engine and a browser? (common GCSE question, name a web browser - google chrome, internet explorer, Tor all get you the marks, google doesn't).
What algorithms does google use? Can you create your own algorithm for searching? What is an algorithm (also a GCSE question).
Cookies, what they are,how they are used, when should you delete them if at all?
Plagiarism - useful for kids to know if they are cheating, lots think changing a couple of words makes something 'theirs'.
Online safety.
This could also spiral off into discussion about Edward Snowden and the US data collection and who the US considers a spy (answer anyone working for a foreign government so teachers in state schools are fair game).
Lots of things that can also be used in other lessons.