No one is abusing the trust system, it is only a negative trust and it should not stop you to trade here on bitcointalk.org ; you have only to use always a valid and trusted escrow.
But it actually does. Look at my tag now because Vod gave me one negative trust. Sure you can look at my feedback and see 20-30 people giving me positive trust but sad that one feedback can hurt u that much. How many people would take the time to look at the actual comment left
It is normal, because no one will click on your trust point and read why do you have that negative trust. However you should contact Vod privately and ask if he can remove it (but I have read in his signature "Want your negative trust removed?
https://bitcointalk.org/index.php?topic=887515.0" you should wait one month).
ajw7989 locked his MSDN thread and promised to stop selling keys. I have removed his negative trust.