Why is Avast (free) phoning home constantly?

[REDACTED]

Most AV's can do their job without an internet connection.  While you need to connect to get updates, you should not need one open all the time. Windows resource manager and the traffic monitor on my router show a lot of talk back to your cloud at avast.com.
Is this something I can opt out of? How?

[Asyn]

That's related to the stream updates.
You can turn them off, but I wouldn't advice to do so.

[Eddy]

There is no av that can do it's job without a internet connection one way or another.
Without a connection it can't update.

As Asyn said, it is not advised to disable the streaming updates.
It is giving you detection updates that are not in the vps updates.

[Pondus]

Most AV's can do their job without an internet connection.

not anymore ...... that was old style AV, today all AV programs have a cloud they talk with   

and this is the reason.....

Malware statistic   
http://www.av-test.org/en/statistics/malware/

20% of all malware ever created appeared in 2013 
http://press.pandasecurity.com/news/20-of-all-malware-ever-created-appeared-in-2013/