Using studnet work in F2F falls under Fair Use... however, not so certain in online arena...

1. action is ethical if it produces the greatest good for the greatest number

2. action is ethical if it passes the categorical imperative (loosely - what would happen if this action was universalized and everyone did it)

3. action is ethical if it protects rights of an individual

(4) action is ethical if it adheres to virtues

(5) action is ethical if it is fair/just

In order to determine if  requiring a student to publically publish their work is ethical, we can look at it from those three approaches.   In my opinion, the action is
* ethical under number 1 (probably)
* unethical under number 2 because, at it's heart, making students publically publish seems coercive and coersion can't pass the categorical imperative (on the other hand, we require students to do things they don't want to do all the time...  hmmm... needs more thinking through), and
* unethical under number 3 (student right to privacy and right to control disposition of own work is violated because there is no guarantee of copyright protection or privacy in web - even with blogs that have a so-called privacy option.  
* I'm still working out ethics of 4 and 5...

These folks seem to believe that they're doing students a favor by requiring them to post on the web. In theory, and for my own values, I tend to think that they make some good points. On the other hand, imposing my personal values on another is not something I'm inclined to do (intentionally at any rate. I'm sure i've done this unintentionally a number of times)