as a moderator on a commercial security software firewall's user support forum, i am a bit more paranoid about revealing my mailing address or posting links on a searchable site that is open to bots and slurp spiders et al.
posting items and photos of my stuff and discussing them in the appropriate forums is one thing, but if i decide to sell, i'd sell somewhere i did not have to reveal personal details to the world that could compromise my location. it's not tough to find, but i don't go advertising myself either. for similar reasons i'd not want to post prices for my stuff that they could add up to see if it were worthwhile paying me a surprise visit some night. it should be a recommendation, not an absolute requirement.
i also see no reason to not post that an item is now up for auction on e-pray or other site, as long as it is obvious that the poster is a discussion member here and the item auctioned is indeed his, especially if he's advertised it here & no-one has jumped at it.
i have not as yet used the swap forum but am uneasy about 3 & 4. i would go along with them as recommendations, but not as absolutes.
something to prohibit posts until members have a certain number of posts in the discussion fora, to discourage dealers only using the swap/sale forum would also be appropriate. the mods here are smart enough to use their discretion in grey areas, if the rules are too tight, it removes their discretionary powers. in other words, let common sense apply.
i like the caveat emptor bit
and am a firm believer in if it ain't broke don't fix it.