Anti-spam measures for websites [closed]

What are anti-spam measure I should consider before launching my user content website? Some things I have considered:

• Silent JavaScript based CAPTCHA on the register page (I do not have an implementation)
• Validate emails by forcing a confirmation link/number
• Allow X amount of comments per 10 minutes and Y per 2 hours (I am considering excited first time users who want to experience the site)
• Disallow link until user is trusted (I am not sure how a user will become trusted)
• Run all comments, messages, etc. through a spam filter.
• Check to see if messages are duplicate or similar (I may not bother with this. I'd like the system to be strong without this)
• I also timestamp everything which I then can retrieve as a long on my administrator page.

What other measures can I take or consider?

Solution 1:

• Captchas, Stack Overflow/Server Fault combine these with rate-limiting well. Basically if you take too long to post a question, or edit to often, you have to enter a reCAPTCHA code.
• Askimet - basically a "global" Bayesian spam filter, you submit content (comments, usually) via their API, and it says if it considers the content spam or not.
• Regarding disabling linking until you "trust" a user - it depends on the type of site, but perhaps enable linking after 24 hours, or until their content gets an upvote or a reply - that should limit many of the automated register-then-spam bots.