I'm a selfish bastard
Fishing is a sport I like to share with others but hunting is one I prefer to keep to myself and mostly because of the reasons you've mentioned. I'll certainly give my time to help someone learn what to look for and I'll gladly check out someones set up and give advise but my honey holes are mine. This is espically the case if you hunt public land. There are enough variables that come into play without inviting more into the mix.
IMO alot also has to do with what type of hunting you do. If you've want to put someone on a animal to get them into hunting you can put then on a stand that will turn up lots of doe and generally they'll be happy just seeing deer. But if you've got the leg work done and are just waiting for mossy horns to give up a shot I personally wouldn't tell a soul. It's amazing what an otherwise intelegent person will do if you let them in on where the big one is. Common sence and sportsmanship go right out the window when old mosshorns is at stake.
For the record I'm not against putting others on quality animals but I have no intension of giving up a honey hole for someone who hasn't put forth the time and effort to find it thenselvs.