A lot of people replace mattresses and dont even think about if their foundation is proper. Then they come online posting about how xyz is a crappy mattress and starts to sag after only 3 months. Someone asks them what foundation they have it on and its usually silence after that. Or they actually fess up and admit they had their $3k tempur on a semi-flex foundation, or they just call it a box spring because everything is a box spring to most people. I feel like salesmen should be explicit about telling a customer exactly what kind of foundation is required for the mattress they are selling someone.