More harm than good. In fact, even now it is impossible to predict how the development of bitcoin and its ecosystem will continue.
However, this widespread inability to understand the fundamental principles and capabilities of the bitcoin protocol can lead the authorities to decisions that would only harm their economic development without having any effect on criminal activity. One of the most obvious flaws in the patriotic actions of such countries as Russia, which seeks to protect its citizens from terrorists and money laundering, is the simple fact that the government can not enforce its demands.
Bitcoin and other crypto-currencies are completely decentralized peer-to-peer systems. They do not use central servers that can be turned off, there's no way to convict anyone, or even hold them accountable, and even if such an opportunity existed, it would not crush the system.
Simply put, no government in the world can prevent anyone from downloading the wallet application or client for mining and connecting to the Bitcoin network. The US and other developed countries have been unsuccessfully trying to regulate the peer-to-peer network of torrents over the past ten years.
Therefore, anyone who wants to use bitcoins to launder money abroad will be able to buy them from private traders or miners, or even purchase their own equipment for mining to turn their "dirty money" into crypto-coins.
Of course, one can easily imagine the development of the bitcoin industry exclusively in the context of breaking the law - for servicing illegal organizations that can receive much more flexible means for both storing and moving money around the world. This is what governments fear, but they do not understand that one way or another nothing can be done about it.