To help you along, here are some of the points that have already emerged:
> Grumblers are not appreciated and are always put down by the Pollyannas of the world, who view them as defeatists and pessimists.
> Grumbling is constructive; if it weren't for grumblers, hardly anything would be improved because we would all be (or pretend to be) perfectly content with the way things are.
> Grumbling is a kind of therapy.
> A primary, possibly the primary, source of grumbling is other people's stupidity. (I intend to have at least a chapter on "Stupid People.")
> Grumbling is most effective when tempered by humor, albeit often sarcastic or sardonic humor.
> To be effective, grumblers need to be literate; illiterate grumbling suggests lack of intelligence and therefore is rarely taken seriously.
> Debunking nonsense is one of the goals of grumbling, for it seeks to reduce foolish notions to appropriate absurdity.

All of this raises some specific questions:
> How does one deal with those exasperatingly cheerful Pollyannas who seem to feel that we're sick if we aren't happy all the time?
> What are some of the constructive results of grumbling?
> If you're a grumbler, how does it serve you as a therapeutic tool?
> What specific evidence (outside the Darwin Awards) do we have that human stupidity knows no boundaries?
> How does one temper serious grumbling with humor?
> Is it important for grumblers to be literate as well?
> What are some kinds of nonsense that really need to be debunked?

As well as a therapeutic tool, grumbling is a very physical tool, or weapon, for making one's way through and fending off stupidity. It's something like Jesse Holmes' big club. Like any tool or weapon, it is never used indiscriminately by the responsible grumbler. There must always be a good and necessary purpose, and great care must be taken to assure that no innocent onlookers are hurt. The wielder of grumbling must have the strength of knowledge of the facts. Sarcastic humor keeps his grumbling sharp and in top form, enhancing his notoriety. The truly proficient grumbler will have honed his skill until he is as respected as John Wayne by stupid and wise alike. Literacy means magnum grumbling. It can bring about fear or respect in some of the most militant stupid.

Constructive results of grumbling? Call it bragging if you will, but in the end, very observable and measurable increasingly high productivity, profitability, and attraction and retention of excellent employees in my area resulted from being "pessimistic" and "resistant to change". In the meantime, a long succession of CEOs, expensive consultants, and other smiling proponents of optimistic and stupid beliefs and plans bit the dust.

(Think Andy Rooney, not Andy Hardy.)