i would consider that very annoying as a user.

Agreed, considering i'm only a few days in myself.

For new users, is it possible to impose a limit on the length of the first 5 messages (or for the next 24/48 hours following registration)? Perhaps only 512 or 1024 characters, although a more appropriate length could be determined by analysing the majority of spam messages which appear to be long lists of phones for sale etc.

Well... just make any new user to read and agree to disclaimer where "by agreeing to become member, will agree not to post any messages with commercial or business advertising/sales purposes... etc... If found guilty on breaking this rule will agree to pay $1000 penalty on each infringing message to Internettablettalk administrative account... etc..."

Something like that should scare spammers at least a bit, and if someone was caught doing this will give legal justification to go after the offending party... Just an idea, not sure how effective this would be?

I'm a member of a couple different forums that keep new users from posting for the first two or three days. Really keeps the spam down. One of them did the change since I've been a member, it really does cut it down. It also gives real new members a chance to lurk and read, cuts down on the amount of duplicate question threads.

Another technique that I have seen prove effective is to throw posts from new users into a moderation que to be reviewed before being posted to the site. Allow senior members of a board to review this que. Once users reach say 3-5 valid posts, their posts are no longer thrown into moderation first and are simply posted directly to the site.

The solution is simple. More moderators. That's it.

That wouldn't stop the posts though. They would just maybe get deleted faster.

A moderation queue and/or limited message length for the first 48 hours might be the only solutions... some spam posts are not from bots but humans in which case even a captcha image won't prevent them from succeeding.

I don't like the idea of preventing new members from posting at all for the first couple of days - that would really annoy me as I often sign up to a forum only when I need to post which usually means I need an answer sooner rather than later. Also, what's to stop a spammer from signing up then returning a few days later to spam the heck out of the forum?

Actually that would be another advantage: most questions newcomers post, can be answered by using the search function or the FAQ. A newcomer who is delayed posting would then first do his homework before he can participate at discussions.

Spammers normally want to spam now and not later. They quickly move on if there are some obstacles to their spamming.