The network marketing industry, despite its 50-year history, and currently a billion dollar business worldwide, is still much misperceived and misunderstod by many. From its beginnings in direct selling, it has evolved tremendously with many variants and innovative models to include affiliate marketing, multi-level marketing, e-commerce, referral programms etc.
Those who are little informed, or have dabbled a little in it but have not been successful and given up early in the game, could deem it a business model that cannot work, or worse still, a con job, a scam, a get-rich-quick scheme, without having the full knowledge and understanding of this industry's concepts and what it takes to succeed in it.
Like in any business, there are of course unscrupulous players which truly tarnish the image of the industry or go all out using unethical ways to beat competitors.
And with the Internet, it's even easier to let the whole world know what you think and feel. Most times, the negatives are played up by people with grudges, disgruntled customers, unprofessional competitors and people who simply love to comment about anything and everything. Just try googling "scam Amway", or NuSkin, LampeBerger, and the thousands of other network marketing brands and you'll have a field day reading about what these people think.
What's important is to know what to believe when you read such stuff and to base your judgment rationally using proper knowledge of the industry or the particular company you have an interest in.
Research on the company's corporate background, financial standing, certifications, business affiliations, legality of its business etc would help too to ensure you are investing or participating in a genuine business.