The US Supreme Court refused to hear an appeal from a New York decision allowing the state to collect sales taxes from Amazon.com and Overstock.com customers, even though the companies have no physical presence in the state. The New York court held the companies had a sufficient presence in the state because of affiliated independent sites that linked to the retailers in return for a commission. See http://nyti.ms/1c7r43i for the New York Times story.
How does this affect mergers and acquisitions? Companies that have affiliate marketing programs will be less profitable, and the value of a company is a function of its profits. Warehouse locations in states without sales taxes will also be less needed by Internet retailers, if similar state sales tax nexus laws are upheld on appeal.