I used to teach college classes back when the Internet was pretty new, and the garbage the students would use as sources was mind-blowing. It is always good to remember that anyone can put up anything on the Web; that doesn't make it true. At least with published books (not self-published), some publisher and/or editor somewhere had to say, "Yes, this is good. Let's print that." There's nothing like that on the Internet.
With that HUGE caveat, however, I love Wikipedia for factual material that is not controversial, like what the difference between granite and marble is, say, or what defines a hypergiant star.
The live links to sources and further material on the topic can be extremely useful and are *right there*. So easy!
Anything that might prompt any sort of fight? I don't look at Wikipedia. Even info about colleges is ripe for changes from collegiate rivals. And the battle over the Sci*nt*logy page is legendary! They finally shut that one down, I read.
And finally I am extremely wary about *any* Internet source for medical advice. Even relatively respectable sources make me skittish. I don't know their biases or who pays their bills. Waaaay too many people turn to Wikipedia for medical advice, IMHO.
