I think it's a complex issue and it's hard to know anything without having the full context.

I think Obama is somewhat conflicted over the balance and is unable to reveal the interesting parts of that question.

Assuming an environment where all digital information is monitored and it actually is used in a reasonable way (active, investigations, internal warrants from courts, etc.) I could see there being an argument that keeping the extent of it secret prevents people from knowing what's being monitored and avoiding those methods of communications. I don't agree with this argument primarily because things change in leadership and governments and having a system like this (especially with it being secret) can lead to abuse.

This was Snowden's point about changes in policy and 'turn key tyranny'.

Clearly access to this information changed Obama's opinions pretty severely - there must be a lot we don't know.