I think that there is an assumption by many .NET developers that, with the CLR's garbage collector, they are immune from memory leaks.  This is hardly the case.  When writing WPF applications, there are a number of gotchas in this department.  Hat's off to Jossef Goldberg, who has a fantastic post on some of the more pernicious WPF memory leaks: how to avoid them and, if that fails, how to find them.