Our project is a catalog of B2B goods. There are 2 types of companies: free and paid. The problem is that 'free' companies cheat and create one more company with another name and contact data. They do that to fill completely category with their goods. Nevertheless 'paid' goods are listed above 'free' goods in catalog.
I thought about identification by:
- cell phone with sms confirmation (cons: only small companies know what number they can fill in);
- card number (cons: also is good only for small companies);
- corporate e-mail (cons: even big companies in our database have no web site).
How would you do? Maybe I am wrong in my suggestions and it might be done in another way.