The majority of GCHQs recruitment is done at a graduate level and I expect most graduates don't give too much thought to the moral implications of GCHQ's mission. If you ignore the moral questions of GCHQ's role, most of news.yc can see why GCHQ is an interesting place to work. Everything is available there: 'big data', processing data at line speed, security work in CESG, building custom hardware, crypto work, liaison with industry, involvement in operations etc. Hell, there's even lots of J2EE development to keep you occupied.
I think the question of targeting populations is perhaps missing the point. Only a tiny minority of GCHQ is actually aware of what we are capable of (and I include myself in the unwashed majority). For example, only a tiny number of people are briefed onto BULLRUN, most analysts are (were) unaware of where that data actually comes from. And an even smaller number are privy to how that data is actually acquired. I perhaps sound like I'm dodging the question but I don't think most employees of GCHQ feel like they are "spying [on] the population". They are simply getting on with their job (something something Godwin). Although Lobban's performance at the ISC public hearing was pretty woeful, his point about needles and haystacks is still valid; we simply haven't got the man hours to find the needles, nevermind go trawling through the haystack.
"post-Snowden" is certainly interesting :)