There have been some notable application-specific hacks applied, at least in previous generations of Windows. SimCity comes to mind: it used memory after free and Windows... 95(?) broke it, so a hack was put in place to explicitly allow processes named simcity.exe to use memory after free. Or something like that.
What people miss from the story is why it was so important that Microsoft do that (and it's a similar reason to why Linus insists on never breaking userspace).
