You mean name it with something that isn't used as a tag?  I guess we could do that or just have a configuration option for what to call the backlog column separate from the rest of the tags.  Once there is a settings page it shouldn't be too hard to do it either way.

That said, if there was a settings page it may be odd to have it in columns since everything else in there would have to be validated as an existing tag. (hopefully)