I've only done it for a very brief period, while selecting from 2-3 available campsites in the area. We often have radios, and very quickly remove the packs from the site(s) not chosen.

I've only done this at vacant sites. I would never intrude on a party at a campsite, and ask to leave a pack. Guess I'm not that concerned that I might lose the site, if I want it. If it is obvious they are leaving, then I just wait until they leave.

I've never done it and gone fishin'. If I plan to stay, I will set camp first, then go fishin'.