Since 6.1 hit everyone has been excited to find out who has what in their garrison. People have been looking for traders, Harrison Jones, or Kura! And it's great that you can share them - people look for them on trade channel, advertise in the group finder tool and these days it's quite easy to get an invite and people seem quite happy to share. That's very nice and community minded of them!
But we did have some funniness about sharing the quests. Someone in guild would say they had it and then we couldn't get the quest when we went to their garrison even though the quest person was there. At first I thought it was a glitchy thing that would fix with a relog or zoning out of the garrison but that didn't fix it when we tried it this morning trying to get the Harrison Jones quest from Madcow's garrison.
Then later in the day I got it from Luxy's garrison but when Aimei and Faith tried to get it they couldn't get it. Luxy was out of her garrison when she invited them.
And then she hearthed back to the garrison and they could get the quests!
So the moral of the story is: be in your garrison if you wish to share your quests! Oh, and btw, it annoys me that the quests are not sharable, but I guess that's just something we have to live with.