I think the default network is pretty solid now. If anyone leaves some questionable feedback it is openly dealt with here in meta. I just think that the scores are too high and will give newbies a false sence of security. If you are new and see some guy with a +10 trust score you assume he is trusted... I think the new formula is alright just the numbers are too high.
Again, an high dark green trust score doesn't mean that the user is pretty "trusted"... everyone should (always) trade with his own diligence. Now this little modification of the trust system will be evaluated in the next few months/years. If someone 'can' suggest a new better thing I think theymos will modify the system another time.
It does not matter what it should be, it matters how it is. Most people just use default trust and rely on positive trust scores to judge someone here.
'Not exactly' when you register a new account you notice that the trust list contain only the DefaultTrust user (it is an automatic thing). So yes most people use DefaultTrust because they feel 'it' correct but it is not always good... see the few people removed in the last months.
PS: it is matter what theorically should be... I always check the history of an user before trade with him (Also if he has +400 as trust score, it doesn't matter
.... whne the majority of users will start to think in this way I am sure there will not be scammed users anymore).