I think multi-level marketing companies are a mixed bag. They are great in terms of providing you with a pre-packaged business model at a dirt-cheap price. People can put as little or as much time they wish into their business. They have a low cost of entry. The tax benefits of the home office can be massive.
The bad side of MLMs is that (depending on what they are selling) the company has almost full control. If the company is selling only one specific product, your business can be gone overnight if the company goes under. The company usually keeps your contact list and all databases. The client list is the real value in any business.