Generally speaking, it is smart public policy to shield prosecutors from lawsuits when it comes to determining in which cases they'll pursue charges...Actually, it's past time. The absolute immunity doctrine should never have been established.
But you could make a good case that absolute immunity takes this idea too far. Even police officers are given what's called "qualified immunity" from civil rights suits, which in 1983 the Supreme Court determined meant, "insofar as their conduct does not violate clearly established statutory or constitutional rights of which a reasonable person would have known."
That sets a hurdle for lawsuits against the police, but not a wall (some would argue that this hurdle is also too high). It might be time to consider applying that standard to prosecutors, too.
The simple fact is, freedom depends on responsibility and accountability. You just can't have one without the others.
Having "Only Ones" impervious to the laws the rest of us are bound by is the essence of tyranny.
And as for incentives for prosecutors, the incentive ought to be to reduce prosecutable "offenses."
[Via Carl S]