http://wiki.answers.com/Q/What_is_ambient_or_stealth_abuse
This is a very tricky tactic used by an abusive person to make you crazy. Since ambient abuse can not sometimes be visible the victim may believe they are so bad and or are going nuts. The abuser may want to isolate their victim from other people as they provide the partner with reality checks such as feedback and reference points. Since their main goal is to de-stabalize the victim's reality they try to ruin these "outside influences." They may gossip about their partner to people in a manipulative manner such as pretending to be concerned for their well being as their partner is acting a little nuts. They wont give there self away to other people, they are calculated in their interactions. People may start to wonder about the partner as the ambient abuser fills their minds with distortions and the abuser apparently my come across as a nice person.
Ambient abuse is the stealth, subtle, underground currents of maltreatment that sometimes go unnoticed even by the victims themselves, until it is too late. Ambient abuse penetrates and permeates everything - but is difficult to pinpoint and identify. It is ambiguous, atmospheric, diffuse. Hence its insidious and pernicious effects. It is by far the most dangerous kind of abuse there is.
It is the outcome of fear - fear of violence, fear of the unknown, fear of the unpredictable, the capricious, and the arbitrary. It is perpetrated by dropping subtle hints, by disorienting, by constant - and unnecessary - lying, by persistent doubting and demeaning, and by inspiring an air of unmitigated gloom and doom ("gaslighting").
Ambient abuse, therefore, is the fostering, propagation, and enhancement of an atmosphere of fear, intimidation, instability, unpredictability and irritation. There are no acts of traceable explicit abuse, nor any manipulative settings of control. Yet, the irksome feeling remains, a disagreeable foreboding, a premonition, a bad omen.
In the long term, such an environment erodes the victim's sense of self-worth and self-esteem. Self-confidence is shaken badly. Often, the victim adopts a paranoid or schizoid stance and thus renders himself or herself exposed even more to criticism and judgment. The roles are thus reversed: the victim is considered mentally deranged and the abuser - the suffering soul.
There are five categories of ambient abuse and they are often combined in the conduct of a single abuser:
I. Inducing Disorientation
The abuser causes the victim to lose faith in her ability to manage and to cope with the world and its demands. She no longer trusts her senses, her skills, her strengths, her friends, her family, and the predictability and benevolence of her environment.
The abuser subverts the target's focus by disagreeing with her way of perceiving the world, her judgment, the facts of her existence, by criticizing her incessantly - and by offering plausible but specious alternatives. By constantly lying, he blurs the line between reality and nightmare.
By recurrently disapproving of her choices and actions - the abuser shreds the victim's self-confidence and shatters her self-esteem. By reacting disproportionately to the slightest "mistake" - he intimidates her to the point of paralysis.
II. Incapacitating
The abuser gradually and surreptitiously takes over functions and chores previously adequately and skillfully performed by the victim. The prey finds itself isolated from the outer world, a hostage to the goodwill - or, more often, ill-will - of her captor. She is crippled by his encroachment and by the inexorable dissolution of her boundaries and ends up totally dependent on her tormentor's whims and desires, plans and stratagems.
Moreover, the abuser engineers impossible, dangerous, unpredictable, unprecedented, or highly specific situations in which he is sorely needed. The abuser makes sure that his knowledge, his skills, his connections, or his traits are the only ones applicable and the most useful in the situations that he, himself, wrought. The abuser generates his own indispensability.
III. Shared Psychosis (Follies-a-Deux)
The abuser creates a fantasy world, inhabited by the victim and himself, and besieged by imaginary enemies. He allocates to the abused the role of defending this invented and unreal Universe. She must swear to secrecy, stand by her abuser no matter what, lie, fight, pretend, obfuscate and do whatever else it takes to preserve this oasis of inanity.
Her membership in the abuser's "kingdom" is cast as a privilege and a prize. But it is not to be taken for granted. She has to work hard to earn her continued affiliation. She is constantly being tested and evaluated. Inevitably, this interminable stress reduces the victim's resistance and her ability to "see straight".
IV. Abuse of Information
From the first moments of an encounter with another person, the abuser is on the prowl. He collects information. The more he knows about his potential victim - the better able he is to coerce, manipulate, charm, extort or convert it "to the cause". The abuser does not hesitate to misuse the information he gleans, regardless of its intimate nature or the circumstances in which he obtained it. This is a powerful tool in his armory.
V. Control by Proxy
If all else fails, the abuser recruits friends, colleagues, mates, family members, the authorities, institutions, neighbours, the media, teachers - in short, third parties - to do his bidding. He uses them to cajole, coerce, threaten, stalk, offer, retreat, tempt, convince, harass, communicate and otherwise manipulate his target. He controls these unaware instruments exactly as he plans to control his ultimate prey. He employs the same mechanisms and devices. And he dumps his props unceremoniously when the job is done.
Another form of control by proxy is to engineer situations in which abuse is inflicted upon another person. Such carefully crafted scenarios of embarrassment and humiliation provoke social sanctions (condemnation, opprobrium, or even physical punishment) against the victim. Society, or a social group become the instruments of the abuser.
Addendum (by a different poster) VI. Cliques of Bullies
Of course, ambient or stealth abuse and manipulation can exist in the context of any kind of relationship and intimacy whatsoever. However, sly abuse of power and underhanded manipulation, with bizarre paranoid malicious gossip and all manner of Sadistic instigators and their eager and foolish proxy pawns, are only all the easier given distance, even shunning and social isolation as experienced by targets of relational bullying and harassment, scapegoats, dissidents and whistleblowers.