The supply of codes in dw_codesharing is getting low, and codes get snapped up just about as fast as they get posted, particularly if they get posted with a convenient link. My favorite trick is to copy the whole list of codes from the http://www.dreamwidth.org/manage/invitecodes page, and paste into the RTE.
Antispam looks at least vaguely sane. The faster they're reported, the faster they're banned. If someone hands you a link that looks like they sneezed when registering their website, it's probably spam; if someone offers to market your website for you, be careful that you're not hiring a spammer to blast your good name across the web and tarnish it. Even (particularly!) if they swear they don't spam, they just email potential clients and insert your link into relevant forums.
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