To be honest, it's mostly "accurate" because the descriptions are so vague that they could apply to just about anyone (and because the human mind is quite good at focussing on the parts that are right and ignoring the parts that aren't).
I recall hearing about an experiment that was done once, where someone gave out a bunch of horoscopes that they claimed were personalised to an entire class, and asked them if they thought it fitted. Then, when most of the class said it did, they told them to look at each other's horoscopes, only to find that they were all identical.
Although, speaking of that, it claims that I am "social, funny and outgoing", as well as charming, which is 100% wrong (I got Otter), so....