A neighbour had a border collie when I was a kid. The dog loved to run so much that it actually created a footpath all the way around the outer perimiter of a 1/2 acre backyard. I mean a real trail, grass completely dead in a stripe, just like lots of human foot traffic does in a park.
That dog also proved that a fence like this:
...was not enough to keep a border collie in the yard. I remember helping to build the fence - we stuck a bunch of round 6" diameter posts in the ground, then stapled that fencing to them. Right after we were done they let the dog out, and he ran full speed at the fence, tucked in his legs and went right through one of the holes. Owner looked like he wanted to kill somebody.
He chose that type of fence so it would be easy for people to climb, because his son and I were friends and our houses were back-to-back.
In the end he put chicken wire up on top of that fence.
This dog really didn't seem to be too interested in people unless they were running. I remember them putting in an inflatable pool, and the dog didn't seem interested in that either.
That dog eventually went a little crazy and started getting agressive with the father. He had to be put down.
That about sums up my border collie knowledge.