I have an assignment in which students are to research some basic facts about common chemicals using Wikipedia.
I was startled by the reaction from my students. They've been told by previous teachers that Wikipedia is "unreliable" and they should never use it.
I've gotten the same reaction from them when I tell them to Google an answer to a question instead of asking me.
I don't believe that Wikipedia or Google are perfect. They each have weaknesses that we must be aware of. But they are useful and powerful. We should be teaching our students how to use them properly instead of just banning them.
Teach students how to find the "Simple English" language page as this is often much easier to read when dealing with complex topics.
Have students attempt to write articles on Wikipedia and they will discover how difficult it actually is. (The first article I ever wrote lasted all of 10 seconds. It took 5 or more revisions before it actually passed the criteria to be a Wikipedia article. It still has warnings on it and is only a quarter of the size of the original article. You can see it here if you want.)
Have students find errors on Wikipedia and correct them. (If they can!)
Teach students Boolean logic (Or just to use the advanced search tools!)
Show students examples of the sponsored links that are paid for so that they arrive at the top of searches.