I suppose that test mercenaries could instead spend this time creating presentations and spreading the gospel of developer testing. Something tells me, though, they are better able to achieve their goals by working with a team rather than preaching to it. A development team that has had the help of a test mercenary ends up with improved code and more tests. It also witnesses the benefits of an additional focus on developer testing. This works wonders in motivating those on the Scrum development team to continue the effort after the mercenary moves on to another team.
