I wouldn't exactly say those are the norm, but I know what you mean.  They're sort of to be expected and aren't something to panic about, and if you've been watching bitcoin for long enough--or have owned it long enough--those kind of price swings shouldn't shock you.

Bitcoin definitely could crash by 20% or more, but I'd expect that after a big rise, sort of like we saw in the summer of last year.  Anyway, this prediction is about as good as the rest of them--useless IMO and not something I'm going to act on.  I don't think I've bought or sold bitcoin or anything else based on someone's prediction.  They're almost entertainment more so than anything else.