I guess this is more of a general StackExchange question... For many years, MathGroup has been an excellent resource to ask the kind of questions that now can be asked on this site. However, MathGroup has been a moderated group, leading to a ~1 day delay between questions and answers. The reason given for that has always been (and I believe it!) that this procedure is in place in order to avoid spam. So my question is: Why is there no spam on SE?


The main reason is that the community itself takes responsibility to identify spam and flag it for a moderator to clean up.

This answer from the meta site on StackOverflow explains more.

This other question was closed as a duplicate but has some useful additional information.

In the unlikely event that you do see some spam, you can click the "flag" link under every post.

If you aren't sure, you can always ask about it here on the meta site.

  • Thank you! In particular the links you provided were quite informative!!! – Thomas Jan 26 '12 at 10:12

SE sites do get spam; there is however a system in place where if a post is marked as spam by five users, the post is automatically removed.


Flagging and closing, if found to be helpful by the moderators, contributes to your flag weight. The current value of this quantity is listed in your profile (not sure about new users and beta). The more flag weight you have the more flags of yours draw the attention of the moderators.

A number of badges you may get is connected to this flagging activity, so there are quite a lot of people actively looking for posts to flag (check the Review link in the top of your screen to find suggestions for reviewing). Most spam posts are deleted within minutes this way.

  • 2
    Flag weight went away, it is now just accumulated helpful flags. – rcollyer Jan 26 '12 at 15:18
  • One wonders how many viable (non-spam, that is) posts are lost to overactive flagging. Getting rid of flag weight is probably a good step toward removing this incentive. – Daniel Lichtblau Jan 29 '12 at 18:06
  • @DanielLichtblau A typical detection theory, false alarm vs. misses, issue. If you don't want genuine posts to be flagged too soon than you need to be soft on spam and vice versa. – Sjoerd C. de Vries Jan 29 '12 at 20:21
  • @Sjoerd C. de Vries Understood. My only point was that adding a points incentive to flagging might be counterproductive. Getting rid of spam is good motivation in and of itself, whereas giving people a reason to be overly zealous about it might cause trouble. – Daniel Lichtblau Jan 29 '12 at 22:35
  • @daniel Well, there used to be a check built-in into the system. If you flagged wrongly it would cost you considerable flag weight. You really had to take care. Especially in the last 50 or so of the 750 points (in the old system) each accepted flag gave you something like .1 point but every rejected flag would cost you 10 points, So 100 times as much. That really hurts. I don't know if they are doing something similar in the new system where they are only counting the number of helpful flags. – Sjoerd C. de Vries Jan 29 '12 at 22:47
  • @SjoerdC.deVries: my understanding is that flag weight, or something very much like it, is still used internally to prioritize and weight the flags; flag weight just "went away" in the sense that it's no longer used as the user-visible measure of how good you are at flagging things. – Isaac Jan 29 '12 at 22:49
  • @DanielLichtblau: Flag weight and the badges that went with it only incentivized flagging that moderators or perhaps sufficiently many other users agreed was correct and disincentivized flagging that the moderators or community disagreed with. – Isaac Jan 29 '12 at 22:53
  • @Sjoerd C. de Vries Okay, I guess that sort of disincentive for malicious flagging was probably more than adequate to meet my concern. Your remark "so there are quite a lot of people actively looking for posts to flag" had me a bit concerned. As long as there is a check on the exuberance of erstwhile flaggers, I guess not much harm is done. – Daniel Lichtblau Jan 29 '12 at 22:54

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