While I don't know a huge amount about the technical stuff behind this if the 'dust' transactions are what I think they are then I think they should be kept, my reasoning being that one of Bitcoins main features are that it is easy to divide, if you restrict that then it becomes less useful and convenient. Then again, I could be entirely wrong and this is something completely different to what I'm thinking off, I was thinking that the restrictions were about people sending 0.000005 BTC amongst themselves or something.