I returned here after a bit of an absence to discover a big (for me) reputation subtraction for "serial up-voting". I've read some other posts explaining what this is supposed to be for, but none of what's described there seems to correspond to me. What is the subtraction for?
There have been a number of changes to the mechanics underneath the reputation system recently. You can find the details in the SO Meta Post Recent Reputation History Changes.
Serial up-voting and down-voting is the Stack Exchange version of stalking behavior. The algorithms that manage reputation irregularities now look for a series of votes in one direction to one account from one or a very small number of accounts in a short period of time.
Another post on the same issue shows an example:
That's 7 upvotes you received within 60 seconds. That's an average of 1 vote every 8.5741428 seconds...if all those votes were from a single user, then that's serial upvoting and those votes are not valid. The system was correcting that.enter link description here
It should work the other way as well - if someone down-votes a set of your posts in a short period of time those down-votes would be ignored and not impact your reputation.
A 25 point change isn't much and I looked and didn't see any particular day that corresponded, but one of the other mods may know better how to see that kind of activity.
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That makes sense as a policy, but I don't see where in my history the upvotes occurred. – orome Mar 23 '12 at 4:12
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1That's what I meant when I said I "didn't see any particular day that corresponded." But I'll poke the other mods and see if they notice anything. – Gary.Ray♦ Mar 23 '12 at 16:25
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After talking with other mods, and looking at the admin tools, the best I can tell you is that it looks like one particular user made 7 quick up-votes and those got removed. It doesn't look like those were all to you, so some other users had a few points removed as well. I can't see the day or the questions/answers that were affected. – Gary.Ray♦ Mar 23 '12 at 18:49
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Hmmm, sounds broken. It's a good idea for a policy, but if it's this opaque to the people affected by it, it's not working. – orome Mar 23 '12 at 20:01
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I suspect the opacity is somewhat intentional, so that people can't easily game the system. – freiheit♦ Mar 24 '12 at 1:15