What's the reasoning behind allowing old trust ratings to be removed/altered?
This effectively erases the trust history, letting users change their ratings once an account has been spent (used in a scam & no longer valuable).

Consider this scenario:

1. Being a trusted member, I lend my trust to a scammer.
2. The scammer scams, as scammers do.
3. Upon the completion of a scam, I remove my trust rating, changing it from positive to negative.
4.
5. PROFIT.

Take this account, for instance: https://bitcointalk.org/index.php?action=trust;u=20968


A hero member, all feedback bad. What's to say it wasn't all good before, perhaps from the same users? Any way to check?
*Not suggesting that in this instance ratings were changed after the fact, just using it to illustrate a hypothetical.