[blcknight]

It could be minimum key size and such, or potentially a specific older version of GPG if NSA ever managed to get something into the codebase, but I suspect it's simple.

Glenn Greenwald is really not very technical at all, so I imagine it was really about getting GPG installed and an appropriate plug-in for his mail client. I actually bet most of the e-mail was spent explaining why he needed to do this, because even now people are still reluctant to use GPG. There's been no explosion in it's use. People are still lazy.