I think it's because it's 1) has gotten a lot of attention BECAUSE it's Nintendo/Pokemon, 2) BECAUSE there have been issues of people hurting themselves, getting mugged, finding a dead body (remember wiihaveaproblem.com?), and 3) BECAUSE it is wildly successful, and there's always some sort of backlash for that.
That said, I haven't turned it on in 2 weeks, and I don't suspect I'll bother with it for a while yet. I played it a good long while when it came out, but where i'm currently located has barely any pokestops, and the gyms that do exist clearly have people who do nothing but play the game or have put real money into it.
Neat diversion, but not for me.