Some changes are made in the rep system today seeing the complaints:
Now the rep power will increase at 2000 per post rather than 1000. So all of you will see a decrease in your total rep power as well as negative rep power from now on.
Also there is a cap on maximum rep power set at 50. So other than admins no one can have a rep power higher than that. That will also limit the negative rep power.
This change was made seeing the repping games and rep abuse cases recently. Other than that you can report in case of genuine rep abuse.
When reporting, please remember that just like people can give you positive rep they are allowed to neg rep if they don't find your post up to the mark. However if it is being used to troll, harass or other malicious intentions and your post was genuine one then (only then) it may be classed as rep abuse.