All Scrum team members must be committed 100% to the Sprint goal of their team. If people are trying to be on more than one team, then they are not able to be fully committed to the goal of either team. This means that neither team can be fully committed to the deliverables of their Sprint Plans. Failure to commit to the Sprint goal results in failure to deliver and a failed Sprint. When people are working on more than one Scrum team, the teams are being set up to fail at Scrum. This rule is often counter-intuitive to traditional project management, which tends to be obsessed with resource utilization. The problem with managed resource utilization that this rule of Scrum solves is the complete lack of commitment that it forces onto the people doing the work. Scrum creates a sense of ownership of the delivery of the whole product in each and every team member when they are allowed to work with one Team.