Yes, just this semester I tried implementing del.icio.us into my ENG102 (research) class to help students share their research with each other. I wouldn't say it was a huge success, but I still believe it is a worthwhile assignment. The main problem was that many students are not familiar with social bookmarking and can't see a need for it. Students tend to "live for the moment" meaning they search for something in Google, find what they need, use it for whatever purpose, and then they are on to something else. It's hard to get them to think in terms of "saving" for later or even sharing it with someone else. I also had to teach students how to download the bookmark extensions for the browsers in class and how to use the extension. This is all time consuming.
The assignment was based around a unit theme for the course, personal freedoms. This was an exploration assignment to get ideas for topics that fit into the theme. We used the notes section to practice summary skills. They wrote 3-5 sentence summaries of what the web pages covered, and we used the tags section to come up with keywords related to the topics. They could later use those same keywords to do further searches for periodicals and books. A requirement was that one tag must be: personal+freedoms. By using this tag we created a repository of web pages on the topic of personal freedoms, which then becomes a starting point for students exploring a topic to research and argue. Here is a list of our collection: http://del.icio.us/tag/%22personal%2Bfreedoms%22
We needed to spend more time on the tagging and keywords. They did do very well there.
I then used the RSS feed to port the collection into Blackboard, explaining to students that they could view the collection right from there, and whenever anyone added more to it, it would automatically repopulate with all the new content.
The evaluation part came in later. We were only concerned with gathering and sharing ideas with that assignment. The next assignment was to choose a page from the collection and evaluate it. The lecture discussed how web sources are not always reliable and are not always the best for college papers. My guess was that many of the pages collected would not be great sources, so an evaluation would point out some major flaws. They were then asked to search and share again, armed with this new knowledge, but I'm not so sure the second batch of pages collected were any better than the first.
I hope that explains it. If you have any specific questions, feel free to ask. I'm already think of better ways to do it next time.