kalfini is correct, you have to report all income. However, we do not get a W2, we get a 1099 form.
I did a wee bit of research on the IRS website and, from what I can tell, we do not need an EIN to be a shopper which goes back to my questioning of why Trendsource (we can mention company names as long as we don't identify their clients). So, here's the questions asked when trying to decide whether you need an EIN:
Definition of an EIN: "An Employer Identification Number (EIN) is also known as a Federal Tax Identification Number, and is used to identify a business entity."
Do you have employees?
YES NO
Do you operate your business as a corporation or a partnership?
YES NO
Do you file any of these tax returns: Employment, Excise, or Alcohol, Tobacco and Firearms?
YES NO
Do you withhold taxes on income, other than wages, paid to a non-resident alien?
YES NO
Do you have a Keogh plan?
YES NO
Are you involved with any of the following types of organizations?
Trusts, except certain grantor-owned revocable trusts, IRAs, Exempt Organization Business Income Tax Returns
Estates
Real estate mortgage investment conduits
Non-profit organizations
Farmers' cooperatives
Plan administrators
None of the above questions apply to mystery shopping. So, the question remains: why does Trendsource need their shoppers to have EINs? What IRS requirement are they trying to circumvent?