First, I want to comment on how you would determine what is reliable information on Wikipedia and what is not. I usually look at the references. There is usually a a link you click on to take you to the reference. You can then click on the reference and determine if it is reputable. When you are linking to someone's blog, that is much different than looking at a peer reviewed article. Even magazines and the news do this with bias and manipulate facts to get people to watch. "See how you can avoid dying with this one simple trick, watch at 6...."
That being said, I think since news has become so mainstream on the internet, new sources are becoming too lazy, or too eager, to get the story out first without checking sources. I have read about this too often over the past two years. Writers creating fictional human interest stories, CNN (generally thought to be a reputable source) reporting facts that end up not being 100% factual...You have to consider what the source is, who the author(s) is, the organization and whether they have some sort of agenda. Too often a single incident becomes "a nationwide epidemic".
I would not tell my students that wikipedia is bad, but I have told them to be careful of using wikipedia as a sole reference. I tell them to double check and make sure that the facts are in another reputable source, for example check the reference. I tell them anyone can post anything on the internet. They do believe everything they read on the internet is true, "but I saw it on the internet" which becomes a whole new conversation about Youtube and evidence of ghosts and UFO's.
I hear often "yes, it's true, I saw the ghost, UFO, lights, werewolf etc. on Youtube. There is evidence." Then I have to have to explain about editing tools and software and how anyone can create a video or picture to show anything they want. The Lochness monster has been proven fake by the man who did it yet they believe it because The History channel is has shows on it's schedule that are not true but appear to be with a fine print disclaimer. They had a similar show on mermaids. I spent way too much time explaining that the mermaid show was not real. :But it was on the History Channel!" It's very difficult to make them understand this. Yet, I give them a National Geographic and they bring it to me and ask if it's true.
I do think telling students Wikipedia is bad would taint the experience, and not always necessarily true. There are some very valid resources and unbiased information there. One of the reasons I like to also check Wikipedia is the seemingly lack of bias. That's why I would give them the facts, the warnings and tell them to validate with another reputable source. I think you would need to give them a list of reputable vs. non-reputable sources as well as a discussion educating them on cross referencing.