I think my program had a 90-95% match rate, but I knew 3 people who didn't match for various reasons over the years (couples match, geo restriction, etc). They all were great candidates and it seemed like a fluke to me. Two of them found good alternative internship sites and ended up at great postdocs. One of them decided that the alternatives weren't good enough, finished their dissertation, published some stuff, and got a really good site the following year. All three are highly successful now. I should mention though, the non-match was really stressful and they all reached out for support, which they got in the form of phone calls and other forms of networking.
The other thing that I will say is that this was a program with a solid rep. I am not sure how it is for programs with subpar reputations.