This is a very valuable lesson, not just for students, but for us as teachers and presenters to a middle school child. By the time students reach middle school, they are approaching the age where parents are allowing more freedoms in certain areas. Computers and Internet access are areas where parents feel comfortable giving more rights to their child and an area where they may not be aware of very important guidelines to teach their child.
One area that needs to be shared and reshared with our students is the sharing and receiving of personal information. They are so into facebook and my space, where they freely share facts, names, and identifiers about themselves or post pictures they should reconsider. There are ways to limit access to outsiders, and our students need to have that taught to them. They also need to be aware that less is sometimes better...don't give all the specific details about your life, yourself, your comings and goings. If there is someone reading your facebook as a friend, they already know all these things, AND there are ways to communicate privately on facebook with an individual if more personal information sharing is necessary.
Online commerce may not be as important for students in my class as that of a high school student. There are simple tools and tricks to teach - the visible lock, the hidden costs that get attached as you proceed through a series of "next" buttons to finalize an order, or the importance of not sharing crucial information (SS#, credit card data, etc) with a vendor that is not credible. More important, it will be crucial to help teach how to determine a credible vendor.
There are some legal issues students need to be aware of . . . pirating, hacking, stealing . . . those are terms they may not fully understand. I often find student work very obviously filled with information they have "cut and pasted" into a finished classroom product. While the students tries very hard to convince me they did not do this, the varying type fonts and sentence structures throughout a paper or simply the vocabulary used can easily identify work that is not truly that of the student. Students will sometimes proudly share how they acquired a "free" copy of everyone's favorite game that requires purchasing.
These are just a few areas of importance regarding a student's responsibility towards digital citizenship. The lessons should be ongoing throughout their education, being repeated often during a school year and being revisited as they move on to the next grade.