I'm in the "as long as it doesn't mean features/forums/posts get moved to pay-only, I'm OK with it" camp.
I've seen sites where content that was in public areas has gotten moved to a private paid-members-only area. I can pretty much guarantee if you go that route
there will be a lot of really angry folks - I know a lot of people (including myself) search this forum regularly as system-of-record for lots of great technical articles. If those threads get moved into "premium" content, that would not be a good thing.
It can be a bit of a slippery slope to have "premium" features, so just consider the affect this will have on all the people using it the way it is for so long.
As far as the ads go, AdBlock Plus solves this entirely - in fact until seeing this thread I forgot this site has big annoying ads.
I can't believe anyone would pay money
to a single
site when they can block ads at a global level for free, but hey there's nothing wrong with capitalism!
Now, on the other hand, if you did this via an online Yacht Club and were able to negotiate yacht club reciprocals that helped members out in some meaningful ways while cruising, I'd probably be all over that, if it helped in areas where I am/plan to go...