skud, one of the high-profile victims of the ban, has launched my.nameis.me, explaining the value of such identities online, not least for people at risk of losing their jobs, getting harassed, or suffering other adverse consequences from expressing their opinions or seeking information from others.
Though many have speculated that Google's real interest is in collecting ever more information useful in marketing, the public justification is that people behave better when they use their government names (though Google's policy actually doesn't (1) verify that you are indeed John Crichton, (2) accept many government names if they are unusual, or (3) deal with non-Western conventions, whether orthographical or otherwise, so the justification doesn't make much sense). Here, a founder of Dreamwidth explains why the "better behavior" argument is bunk.
I have tenure, and I'm pretty out as a fan under my government name, but a fannish autonym has real benefits for me anyway, and it's far more important for people who want to participate in public discussions but might suffer if their teachers, students, bosses, ex-spouses, etc. found them online. I sincerely hope Google gets this right, because--as skud points out--it's already affecting search results and other activities outside of Google+.