There are several tips on how to stop accidental deployment of task sequences (one of my favorite links is to a blog post by Frank Rojas). One of my customers had come up with a fairly good idea on this topic I wanted to share also.
Like programs, a task sequence can be set to only run on certain supported platforms. If you have the scenario where you only want a task sequence to be run to a machine which has done a PXE boot or booted from media, you can use this to your advantage. On the task sequence you set the supported platforms to be some OS you don’t have, and don’t expect to have, in your environment. Now, I know that everyone reading this has likely deployed all MS OS shortly after we release them and thus it might be hard to find an unused OS. I suggest checking your inventory and seeing if, oh, Vista is in much use in your enterprise.
What ever you pick, it will limit the task sequence to only allowing execution on that OS and from WinPE. This means you can advertise (only by accident of course) that TS to all systems and have less risk of it accidently running on machines you don’t want it to. Cool eh?