I do not allow my students to cite Wikipedia in their assignments. The main reason that I do not allow this is because I know that all throughout my college career I was told I was not allowed to use Wikipedia. I do not want to get the students dependent on a tool that they probably won't be allowed to use anyway. I've noticed that Wikipedia is the first place that many students look and I truly want to break them of this habit. I try and get them to look for scholarly articles instead. On the other hand, I do tell my students that although Wikipedia is a wiki and anyone can edit it, it still can be a good resource just to find out general knowledge. Using Wikipedia to settle an argument about a celebrities age is different than using it for a research paper.
I use Youtube quite often in my class. I think that students respond well to videos, especially if they are short and entertaining. Unfortunately, my school has Youtube, teachertube, and schooltube completely blocked from the students, unless I play a video for them, they cannot utilize these tools.