DNS is decentralised by design. Run your own server and these things won't impact you. In regards to Namecoin, the network is too small (173 Nodes) to withstand DoS attacks. If Namecoin nodes were Incentivised more people would run them.
Namecoin- Dot-Bit-enabled websites are immune to these problems, because instead of the phone book being a corporation or government, the digital phonebook is on
your own computer. Bitcoin technology ensures that every user in the world has the same phonebook data on their computer, without anyone being able to illegitimately change that phonebook data.(
https://bit.namecoin.org/)
And why do we need a many Namecoin nodes?
