Kind of a cute idea, although if I'm seeing this trail correctly, you wouldn't be starting at the edge of the Facebook parking lot--you cross a hill, then cut through an elementary school, walk a few blocks to Junipero Serra and start up the trail there. Also, the trail itself is not very wooded--more like grassy.
I lived in the neighborhood of Facebook's office for a few years. I suspect the "wooded trail" is actually just walking up to the top of the small hill by Peter Coutts Circle. It's actually a pretty nice view for how short a walk it is. If it's not that, it's the trail to the dish, which is not wooded at all.
Either way, I don't see how you could possibly see Apple in Cupertino from either place. Take a look at the map, and then look at this random video shot from the dish trail: http://www.youtube.com/watch?v=Aar3EH4y1JA
The camera is pointed in the direction of Cupertino around 1:20 or so. There's no way you can "point out" Apple's campus. You can wave in the right direction, but you can do that from an office too.
I live there now and the hill is on my running path (as is Facebook HQ, sadly). Apple is many miles south. There's no way you can see it, let alone Google.
Next time I talk to Nick Bilton I'm going to give him a hard time over this.
http://maps.google.com/maps?q=Facebook+Offices,+South+Califo...