The word Karma seems to have become very much a part of the common language. Non-Hindus and non-Buddhists tend to use it in the negative sense, of someone getting what is coming to them. Essentially, there appear to be three interpretations. The original religious one, regarding consequences from past lives the casual common-use bastardization of just comeuppance for the future as mentioned above and a third use as a shorthand for the concept of cause-and-effect, either individual or general.

Both religious Hindus and philosophical Buddhists tend to endorse a literal conception of Karma as past-life consequences (both positive and negative) as a part of their belief in the Samsara cycle of birth, death, and rebirth:

Just as a man casting off worn-out clothes takes up others that are new, so the embodied self, casting off its worn-out bodies, goes to other, new ones. -Bhagavad Gita 2.22

From a superficially ethical viewpoint, this may seem like a decent way of encouraging moral behavior, in a similar fashion that the threat of eternal torment is utilized for coercion of civil compliance in the Abrahamic traditions. However, just as the threat of Hellfire for nonbelievers expresses a belief in (and support of) a hideously hateful cosmic order, so too this concept of Karmic reincarnation is used to justify the stratification of gross injustice and vicious bigotry in the real world:

Now, people whos behavior here [in life] is pleasant can expect to enter a pleasant womb [after death], like that of a woman of the Brahmin [priestly class], the Kshatriya [warrior class], or the Vaisya [trader and farmer class]. But people of foul behavior can expect to enter a foul womb, like that of a dog, a pig, or an outcaste woman. -Chandogya Upanishad 5.10.7

A belief in Karma may indeed inspire people to behave better (by the standards of their society) if only for their own sake. However, while Karma, in the broad sense, is a belief in consequences, the consequence of belief in Karma, in practice, may also bring complacence regarding injustice in Our world, and/or scorn toward those who are believed to be deserving of their suffering. Since, it is believed, everything happens as a consequence of a past life, it stands to reason that bad things would only happen to bad people. Even the casual use of the word in nontheistic parlance implies a belief in some inevitable cosmic justice (and, by association, an abdication of responsibility of fairness for others in our earthly life). As with other postmortem superstitions, even a casual belief in Karma is a platitude which implies (at best) a moral complacence around achieving fairness through human means in this — our human world (such as an acceptance of the caste-system), and/or communicates a sort of Schadenfreude vicarious satisfaction at the imagined inevitable suffering of wrong-doers (as in the belief in a Hell). While it can be argued that this moral theory regarding afterlife justice may inspire socially acceptable behavior in believers because they will wish to have a better reincarnation, a much more tangibly clear downside to this belief is a path of least effort in accepting that those who suffer somehow deserve their fate and/or that all will be made well by a higher power after death anyway, requiring no real effort from us now. The logical consequence of such (perhaps largely unexamined) beliefs act both as a salve against concern over existing injustice and as a sedative against efforts for betterment.

The most charitable reinterpretation of the Karmic doctrine is a scientifically poetic conflation of karma with the process of cause-and-effect. That is, whether our soul/atman/consciousness reincarnate or not, the actions of peoples past lives really Do have consequences for the lives of future people. Given some combination of the Earths carbon-cycle, belief in Panpsychism, and/or the memetic transfer of archetypal personalities through generations, Karma may then be rescued from the immoral consequences of belief in cosmic justice, and redefined as a history of the moral progress of our collective humanity. If we accept universal consciousness, then to hurt (or allow the hurting of) others, is to hurt oneself. In this way can our very real interconnection be realized, and the excellent ethics of border-free compassion be implemented.