Tbh there's quite a bit of doubt that anything is safe from government agencies. Though Prism might be limited, I'd be surprised if there aren't at least five or six back up programmes.
A good point he makes. Write sensitive information on an unconnected device. Encrypt and send. But even then if they'd want the info they'd get it.
The reality is, you can be paranoid about his, but the NSA simply doesn't care about 99% of the info on the net. Or rather they don't have the resources to care. So your info is quite likely safe, simply because it doesn't meet their criteria, and gets dumped.
If you really want to avoid detection, go back to pen and paper
One other tip I always give people is, make it expensive as hell for them to get your info. One simple way to do that is by creating as much traffic as you can. If people start doing this en masse, it will become less cost effective for agencies to gather data.