People like to steal Pins that are performing well and are being shown in the feed on a regular basis. They will steal Pins that are being marketed well.
Pins that are well branded, are getting lots of traffic, the Pinner is a trusted resource, and their SEO is on target.
So, you might see a Pin from someone you know, like and trust and re-Pin it. Except that particular Pin might have already been stolen and redirected.
You are effectively helping the thief increase his/her traffic.
Always check that the Pin goes where it’s supposed to go.