For a professional, a solid reputation among clients, peers and the online communityis key to success. It only takes one person — an unhappy client, a disgruntled employee, an ex-business partner or significant other, or a desperate competitor — to start an online smear campaign.

Negative or unflattering postings on review sites such as Yelp.com, HealthGrades.com, Avvo.com and Angielist.com, or social networking sites, blogs or chat forums, can do serious damage to a professional’s online reputation, even if they are irrelevant or false. Aggressive online threats and off-putting reviews also can create a nightmare of distractions, worry and expense for the professional.