The level of Geniuses on Net Forums always astounds me!
Why would you make suck a silly statement of fact with out even checking to see if it is correct?
VzwApn service Does NOT control your ability to get mobile data, had you disable it , force closed it then checked, you would have seen that in doing so, neither 3g or 4g service is inhibited in anyway.
What does it do?
Beats the out of me, But I know for a fact it doesn't stop 3g or 4g
Given that it starts of Vzn I assume its Verizon and thus is crap and should not be on a nexus
btc0526 is spot on with his statement. Don't disable it. It may not stop you from having internet service but the APN is typically the address your phone uses to connect to the network. Some services on your phone may cease to work correctly as a result of the service not running. The 1st link below is directly from Verizon and tells you what some of the APN settings are for. The 2nd link is from Wikipedia and explains what an APN is and why it's needed.