Chances are if you received negative trust, it falls under one of the following:
Lets see how accurate your list is....
1. broke a forum rule,
They usually ban you for this. That or give a warning that could eventually lead to a ban.
2. attempting to scam,
Yup.
3. have scammed,
This is exactly what negative trust ratings are for
4. begging,
Nope. This falls under "breaking a forum rule"
5. being a troll
This really depends on how they are trolling. If they are trolling my making/accepting offers they have zero intent on keeping then they are effectively a scammer, mostly otherwise, no
6. send pm solicitations,
This really depends on the unique circumstances. If the circumstances are somewhat shady then yes, otherwise no
7. spams with or without sig campaign
lol, no
8. sold account
no
9. etc etc etc

but no
There are may reasons why to give negative trust, outside of scamming members
That is not the intent behind the trust system.