Zero-cost attack type posibility

[ghost]

As I understand, everyone can create a lot of new accounts per second for a free to make critical queue of the blocks.

The network may go fall with popularity growth. Is protection mechanism available?

[miguelfreitas]

There is a POW required for every new account which it is meant, primarily, to prevent peers from hijacking the username for a registration which has just been posted on the network. So there is some cost involved for creating a lot of new accounts but squatting is definitely possible.