There are TONS of problems caused by this bug and no real use for it besides detecting block updates. I know Mojang is currently planning to ignore the bug, but I would strongly recommend reconsidering.
Not really a bug, as the silk touched leaves are a different block - they still decay when not near logs. This is a useful feature to have and so should not be removed.
rtfm
There are few things I dislike more than when people decide that anyone whose opinions aren't the same are trolls.
But in any case, here are some other things that burn in Minecraft: Minecarts, sand item entities, eggs, snowballs, and sand blocks (after flint and steel is used on it).
Why should the sand entity never appear to be on fire? Every other entity in the game burns, why make an exception? You can make some pretty cool things with it.
https://www.youtube.com/watch?v=QGLiaaN4eqk&feature=plcp&noredirect=1
(I know that video isn't vanilla, but it's the most accessible example of what I mean.)
So will it still burn if it falls through lava instead of just landing in it? If so, that's fine.
This is not a bug, Dinnerbone! Please consider reverting.
And of course compatibility with previous circuits should not be a factor. Leaving the game broken forever to prevent a couple minor circuit changes is never a good idea, especially in the update that exists so that all broken circuits will happen in the same update.