I'm not sure setting an arbitrary target on a certain number of threads to start as an achievement would do anything to help improve the enjoyment of the game. 

Things like thresholds and targets for threads have been used numerous times in the past by various leaders (for both made man positions and CL positions) without it having a positive impact. There are already huge benefits to posting (exp, vision, reputation, etc) and fun to be had from same, so setting specific numeric targets is almost counter productive. In order for the quality of the posts to matter more than the quantity of the posts it requires a far more subjective review than an achievement can manage, so I'd personally prefer to see left the monitoring and encouragement of this area left to us the users rather than to the game mechanics.

This would encourage spam and laziness.

Spam is self explanatory.

Laziness because people that just want the achievements will use any means to get their posts/threads, probably copying and pasting from other places. People already do and have done that even without achievements.

Whilst rewards for posts are nice, this kind of hard coded reward encourages all kinds of bad behaviour (as evidenced by the people copying and pasting song lyrics/menus etc etc all in the pursuit of vision/VIP points).

If you want to reward people for posting yourself, you can always tip them. I find that the best way of showing someone that their posts are worthy of reward, rather than something automated.

Uh but I thought copying and posting was already prohibited and those who did it was jailed or something? Just heard it from a friend not really sure.

It has always been against the rules, yet people will always attempt to break the rules. It is prohibited, but if an achievement is brought in people will attempt to find a way around those rules. They'll simply start copy/pasting and paraphrasing a little more. Or throwing in a few typo's to make it look real. Or copying content from other walled sights where a login is required to access the content. 

It's seeking to reward set numbers, regardless of quality or effort put forward. That's the problem here. 

The positive of introducing it? Not really any. It's only encouraging people that will be posting for all the wrong reasons.

The negatives of introducing it? Read above. 

Arbitrary set thresholds hardcoded into the mechanics of the game aren't a solution to a problem, they're a cause of one. I agree that threads and positive posts should be encouraged and rewarded, greatly, this just isn't the right way to do it. 

Aahh okay :) one more thing satana. .