Elteto.net

As many developers have pointed out, Elgg and MediaWiki functions can be easily replicated in Drupal.

Zacker.org had a great article on the subject:

http://www.zacker.org/elgg-vs-drupal-floss-competition
"Decision makers in Universities IT departments will be forced to choose between adopting Elgg or Drupal instead of being able to invest in a solution that captures the best of both projects."

Well said. True, it is not the intention of Drupal developers to create a monster "everything but the kitchen sink" content management framework, but the duplication of effort is harmful for all projects involved, especially since Drupal modules can provide most if not all the desired functions of some of these other frameworks. Web admins and non-techie education decision makers are confused by the various choices as it is.

I am a strong advocate of Drupal and Moodle integration, as Moodle has a scalable, sophisticated, yet stable structure and it contains such a number of classroom management system specific functions that replicating them with Drupal would require an excessive amount of add-on module development. With database sharing, universal logins could easily be solved, and naturally, both systems are PHP/MySQL based.

And of course, I think Bill Fitzgerald explored some of these issues in his Drupal e-learning book: http://www.packtpub.com/drupal-for-education-and-e-learning/book.