In a free society, people can access information to keep themselves informed. Most folks got themselves out of the path of Katrina, because they heard radio and TV reports about the coming storm.
The ruling junta in Burma didn't bother telling the people in the path of the storm of the danger coming their way, and they didn't have access to other information. The only folks who knew the storm was coming their way were the ones who had access to radio stations beamed into the country, on the order of like Radio Free Europe. The government just flat didn't care how many died.
Even if the government cares, these storms can overwhelm any defences, and if people are in the way, they will die. Can’t blame even the most negligent government for an event of this magnitude. Of course, one can blame them for their poor responses and the general undevelopment of the country.