Re: Boarding and rafting to stranger's boats.
In many locations there isn't a choice. One marine near me has about 100' of sea wall, and that's it. If you get there after its all gone you can either raft, or keep sailing to the next marine about 20 miles away. I promise you if you show up there on any weekend people will raft up against you, and will do so without asking. And tying up a dinghy to the outside will just result in the harbor master kicking your boat out of the marine.
As with most things there is an etiquette to rafting which should be followed, but other than that I can't see the problem.