While we are at it, why not limit the number of negative ratings that one user can give to another? Some sane limit e.g. 20 would be sufficient (AFAIK there has been no case where 10 was legitimately hit let alone more).
Instead of limit, a trust feedback cool down meter can be implemented. You can give only one feedback a day to a specific user. This will help in reducing trust spamming where a user is giving 50 long feedback in a day to a single user.
For length, I like the idea of view more, or fix the length of trust feedback and user who like to write more can create a post and link to the feedback.
How exactly is this a good idea? Mistakes tend to happen when writing or submitting feedback, thus I sometimes send out a rating to a specific user multiple times in a very small timeframe.
-snip-
Theymos has explicitly said
Trust spam isn't allowed
However there's a lot of spam and very little is being done.
He only acts upon it in very extreme cases.