I can see using this when dealing with code that isn't mine. Sometimes you get a really useful library that now and then does something really boneheaded, like die() when it should really be warning, or explicitly committing a transaction to the database when you might still want to be able to roll back. For stuff like that, this technique could be really useful.

However, for cases where I own all the pieces of the code.. why not just make the variable bits variables?