when you have 1000 merit whereas +0/=1/-4 this type a trust increases chances to loose the
http://bitcointalk.org account?
You only lose your account when your account was hacked and you failed to recover it or similarly when you lost your account by yourself and can not recover it (without hack).
Negative trust only affects your account if you want to make trades with other forum users or your chance to be accepted by campaign managers to join signature campaigns.
Learn about Trust / Feedback system.
LoyceV's Beginners guide to correct use of the Trust system.