Small businesses and entrepreneurs are subject to antitrust laws just like large businesses. Antitrust laws generally discourage something called tying or bundling arrangements.
What are tying arrangements.
A tying arrangement occurs when, through a contractual or technological requirement, a seller conditions the sale or lease of one product or service on the customer's agreement to take a second product or service. This can be especially troublesome when a seller has "market power" in a product and uses that market power in an attempt to force customers to purchase a second product.
An example of a tying arrangement.
An example of a tying arrangement may be a book publisher that requires a bookstore to stock up on an unpopular title before allowing them to purchase a bestseller.
Necessity of Market Power
Most small businesses probably lack the market power in a product to create illegal tying arrangements. In these cases, tying arrangements would probably be acceptable under the law.
Avoiding suppliers who try to force tying arrangements on a small business
It may be more common for a small business to encounter illegal tying arrangements as a customer. Suppliers to small businesses may try to force small businesses to buy more of their product line than a small business wants to buy. In these cases, a small business should complain vigorously and should seek legal help if a supplier doesn't change its ways.