Public facing authoritative NS all masters

[Gary Wallis]

DNS experts,

What are the drawbacks, if any, of running only master name servers for 
the set of authoritative NSs?

For example given:

[root at rc37 unxsVZ]# dig latimes.com NS +short
dns1.tribune.com.
dns2.tribune.com.
dns4.tribune.com.
dns3.tribune.com.

Where all 4 dnsN servers are in fact masters (this is just a 
hypothetical, the NS above are most likely secondary servers)

Thank you!