My inaugural post at the brand-spankin'-new Sweet Talk Bleg is available. In it, I treat the right to say "no" as a commodity. If, for whatever reason, a person finds that saying "no" is difficult, it might be a good idea to seek credible prior restraint. Trading the right to say "no" could certainly be euvoluntary.
But there's a difference between a specific and a general power of attorney. When agents of the state get to decide how and when to say "no" on your behalf, your status as a sovereign individual wanes. And it may perhaps wane more than you might like. I encourage anyone who seeks redress from the government to be sensitive about this risk.