Do you think governments are afraid legalizing bitcoin because it's difficult regulating its use, circulation, determining individual's worth, earnings and may lead to tax evasion?
I don't think they are "afraid" (well, we can talk about all governments in one). I believe there is general interest in trying to determinate the legal situation of bitcoin, but is going to take a while. It is not easy to determinate how new "money" is going to fit into the economic system of a country. It takes a lot of bureaucracy, and maybe is going to take more than a few years.
They are not afraid it is just that it is not easy to legalize bitcoin here in the world as it is just new to our system and in our life, and one point that they are having hard time due to many ponzhi scheme that are now out of the market, not only with that, nowadays illegal transactions are using bitcoin as mode of payment.